Give an example that you can understand in the simplest sentence.
No matter who it is, it happened when I was a child. Suddenly I found myself dreaming in a dream, and then I could do everything, fly, conjure up weapons, knock down weirdos and so on.
This is a lucid dream.
There are also ways to exercise lucid dreams, and the most common and effective one is mental suggestion.
You bite your finger 10 times a day, and sometimes you bite your finger in the street.
When dreaming, I will bite my fingers unconsciously, because I am familiar with this habit, but I can't bite in my dream, so I will find myself dreaming.
As for OBE, which is higher than lucid dream, you can Baidu it. I am a practitioner, full of practical knowledge. Of course, I have no lucid dream. This hint of lucid dreams is not very good for people, so it is not recommended that you practice it.