Gotcha = I have got you...and has two meanings: 1. I have (finally) understood you. 2. I have (finally) caught you.

All of the above is correct. Unless one is playing a game or is competing, it is most often said to mean "I understand".

If you say "I've got you" really quickly sounds like GOTCHA and it means (ALWAYS depending on the context) "I caught you" if you made a joke to someone or "I understand you" if you got the idea of what someone is explaining to you. *_*

when you've successfully played a trick on someone