There are many ideas about what lucid dreaming is or isn’t. What I’ve found to be true is that lucid dreaming is when you are aware that you are in a dream. You are able to, in that moment, notice that you are immersed in your dream, and depending on your level of lucidity, change or alter your environment and/or the things you to in it.
There are stages or levels of lucidity within a lucid dream. You can have a low level of lucidity and find yourself easily getting caught back up in a dream because you couldn’t maintain consciousness. And you can have very high levels of lucidity which are synonymous with having an out-of-body experience, where everything can seem even more real than waking life.