The Tao existed long before Lao Tzu is reported to have written it down, when he did so for an admiring army officer. Rather, it is said that he was essentially summarising the collected wisdom of the previous few thousand years. It's essentially open source wisdom.
Afterwards, it was adapted and edited by various sages throughout China. It was eventually declared 'finished' and definitive by Wang Bi about 800 years ago.
Having said all this, none of this is that important—they're only the messengers—the principles inside are what matters most.
The Tao Te Ching is largely compatible with any religions or alternative philosophies that it encounters (e.g. Confucianism and Buddhism) because it is so generic. It applies to everyone, in every walk of life because it is simply the way of things.
Others might call it 'God's Will' or 'the laws of nature'. The Tao is merely the Tao, or 'the way'. We are all on the path, whether we know it or not.
The Tao must be lived, not just read about and discussed.
The best way to look at it, though, is like the forest and the mountain. Life is the forest, through which we can take any path we choose. The forest doesn't care what we do, though—this is just the way of the forest.
We may wander aimlessly for as long as we want, but there must come a moment where we must choose a direction, where we choose to make our way towards the mountain. There are paths that lead to the mountain that have been trodden by those who have gone before us, but we may not be able to recognise them.
The Tao is one of the ways in which we may be guided through the forest.
1 - the only true expression of the Tao is that which is lived, not that which is written about or discussed.
2 - We live in a relative world, there is no thing that is absolute. High reveals low, short shows us long.
3 - A focus on material wealth (as revealed through the concept in 2) will fill the heart with anguish and desire to be more, to want more. Do not show wealth to others, or even yourself.
4 - The Tao is directly imperceptible, infinite and outlasts all. Given enough time, our greatest achievements and wonders and knowledge will all disappear.
'Too many words hasten failure / cannot compare to keeping quiet.'
5 - The quietness of simplicity wins over the unnecessary and burdensome noise and busyness of bureaucracy. 'When utilized, it is never exhausted.'
6 - Life creates life and thus extends infinitely into the future.
7 - Placing yourself last and ending up in front: the paradox of selflessness. If you prioritise yourself and your gains you may win something, but lose much.
8 - Be like water. The nature of water is to flow into the lowest place and find its level. Being like this we respond in truth, we act with kindness to all, we move and change with the world as it changes around us without fighting it.
9 - There is nothing good about an overflowing cup. With achievement and success it is best to discretely step aside, otherwise your hubris will invite problems into your life.
11 - All that is useful does not always have substance. Emptiness, a lack of anything, is important. A doorway, a bottle, an arena - all are useful for the space and emptiness they create.
12 - 'The sages care for the stomach and not the eyes'; constantly striving for greater distraction and speed and wealth can leave us senseless and overloaded. Instead, take care of the simple things in life.
13 - Comparison, approval, fear of disgrace... all bad habits that centre around the ego. If we let go of them and learn to love ourselves in equal measure with how we love the world then we are more likely to make our way more peacefully through life.
16 - Troubles and pain are caused by a discrepancy between wanting things to be a certain way and accepting them as they are. 'Knowing constancy' and the true nature of how the world works is to know yourself and to know/understand the responsibility you have to guide your life with these things in mind.
17 - 'The highest rulers, people do not know they have them'. When in a leadership position, there are some means of leadership that are better than others. The best is for the people to believe they did it all themselves, the worst is to fear who leads them. Act quietly and subtly to the benefit of those you lead.
19 - There are great pitfalls to knowledge. Too much of it, or an obsession with gaining more of it, can hold us back and frustrate us at every turn. It is not enough to grow your knowledge and keep your nose stuck in your books, you have to live your life and get wise that way also.
22 - A position or a view or an argument does not gain strength or additional validity through defense. It merely is. To spend energy defending it is a great waste, instead yield and spend energy on something more constructive than fighting against another who holds a different view.
23 - Sparse, infrequent speech is better than drawn out platitudes. In this respect, we have the agency to choose how we communicate and the mandate to determine our own thinking. Imposing discipline on our thoughts and actions, we can best determine how we move forward in life. We reap what we sow - if we think on loss, we find ourselves losing; if we think on gains, we find ourselves gaining also.
26 - 'Heaviness is the root of lightness'. While a light approach to daily troubles and happenings is a wonderful thing, many of life's challenges should be approached with the required level of gravity. If we approach important things lightly, they will go wrong. We can only be light if we carried the heavy before. Heaviness is the root of lightness.
29 - The world cannot be controlled. Those who would try, fail. Those who would grasp a thing, lose the thing. The wise instead cast off extremes, excesses and extravagances. They know the world for what it really is, a spiritual instrument.
30 - Force and violence beget more of the same. If it must be used, never further than is absolutely necessary. Ideally not at all, ideally never. Instead work with courtesy and calm, consensus and teamwork.
33 - 'Those who understand others are intelligent. / Those who understand themselves are enlightened.'
36 - Pride goes before fall, thus 'If one wishes to shrink it / one must first expand it.' Likewise, you reap what you sow in life: 'If one wishes to seize it / one must first give it'.
38 - Virtue is highest, followed by benevolence, followed by righteousness, followed by etiquette. There is high virtue, and there is low virtue: 'Low virtue takes contrived action / And acts without agenda'. This reminds me of Matthew 6:2, 'So when you give to the needy, do not announce it with trumpets, as the hypocrites do in the synagogues and on the streets, to be honored by others. Truly I tell you, they have received their reward in full.' Those that proclaim their virtuous actions on social media would do well to heed this sort of advice.
39 - 'Do not wish to be shiny like jade / Be dull like rocks.'
44 - 'Excessive love must lead to great spending / Excessive hoarding must lead to heavy loss.' The way of the Tao is contentment and knowing when to stop, and how to let go.
45 - Those that have truly mastered an art or technique do not look perfect or complete to the untrained eye. Their abilities mask the long periods of work at their craft or profession. It is much like knowing someone with 'all the gear and no idea' who does not understand why a professional, using basic equipment, gets far better results. 'Great skill seems unrefined / Great eloquence seems inarticulate.'
46 - 'There is no greater calamity / Than not knowing what is enough.'
53 - Many think there is a quick fix or solution that can shortcut our progress through life, but there is not. That way, says the Tao, leads to barren fields, empty warehouses and charlatans parading their wealth. But this is figuratively and literally bankrupt. Better to grow slowly and consistently through repeated right action than to think you can jump ahead of the queue.
54 - Live the Tao by applying it to life and rooting it deeply. Don't just play with the ideas.
55 - We are in a marathon, not a sprint. Take all in moderation. Lots to consider in this chapter.
61 - Principles that work well on an interpersonal level work well on all other levels. Do not pretend that things change on different scales; it's all human interaction after all. Treat people well on your way up, because you will surely meet them on your way down.
63 - 'Act without action / Manage without meddling'. 'The difficult tasks of the world / Must be handled through the small tasks'. Therefore, never attempt great deeds. Instead, repeatedly do small things very well.
64 - A long journey starts directly under your feet (often mistranslated as 'a single step'.) Proceed at the end as you do at the beginning and your work won't be ruined.
66 - Power and leadership require humility to be effective. 'Those who would be above / Must speak as if they are below / Those who would lead / Must speak as if they are behind.'
67 - Three treasures of the Tao: compassion, frugality, not daring to think yourself ahead in the world. Each in their turn give access to true courage, the ability to reach far and wide and the ability to be a true leader.
69 - Judo and Aikido are based on the words in this chapter. 'I dare not advance an inch, but prefer to withdraw a foot.'
70 - 'The sage wears rough clothing, but carries jade inside.'
72 - Know yourself as well as you can. Neither glorify yourself, nor bottle yourself up. These are extremes that we can push and push and push... but they will ultimately reverse on us and deal great damage within and without.
75 - 'The people's hunger is due to the excess of their ruler's taxation so they starve', much the same with our own spiritual hunger if we tax ourselves too much and spend too much energy obsessed with material wealth.
77 - The Tao of heaven increases the deficient and reduces the excessive. The Tao of people goes the opposite way: to those that have shall more be given, to those that have not shall it be taken away. The wise are those who know when they have enough and are capable of helping others and giving away what they have and not heaping praise onto those who have already achieved acclaim and riches.
79 - Those who give in accordance with the Tao receive abundantly.