You are lucid when you realize within the dream that you are dreaming.....whether or not you choose to change things or not is a matter of personal preferance.....you can be lucid a little (knowing it is a dream but unable to change stuff) or you can be 100% and play "god" and do anything (or you can be 100% lucid but just explore without changing a thing)
I've only had about 2 fully lucid dreams. Othertimes I know I'm dreaming since I'm not in my room but in an old house I used to live or something like that, but can't do anything. The closest time was when I realized I was dreaming and tried to control it. But I was too tired and whenever I opened my eyes, I did a little telekinesis spontaneously on so[?]me items and fell asleep. Was that lucid or not?