Peace on Earth
Laozi came to make this concept in a time of unrest in the civilization of China. The clans fighting the rulers wanting absolute power and things being burnt down, but from those ashes arose Laozi as if he were a Phoenix being born again. He introduced the idea of peace and harmony with nature, The Yin and The Yang, and "If you must rule, rule as little as possible.
The Yin and Yang symbolizes the balance between good and evil. Meaning in good situations there is always a little bad and in bad situations there is always a little bit of good. He got the name yin and yang from the Yin-Yang School of Thought.
Laozi also said that we should have peace and harmony with nature. To me this just sounds extremely hippie, but I also think that it is important to have a balance between the resources we need and conservation of nature. If we don't have peace and harmony with nature then both us and nature won't be happy.
Finally, Laozi believed in if you must rule rule as little as possible. He mostly believed this because before he came up with his philosophy there was a lot of disorder in China because of rulers wanting to rule completely. So ruling as little as possible would help that problem.