When do you say "Gotcha." ?

Question

When do you say    "Gotcha."  ?

Answer

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

Answer

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

Answer

As an entire phrase?

Usually when you have successfully tricked somebody, or something like that.  Another possibility is when you're trying to hit something and finally do.  There might be other situations too, I'm drawing a blank (there's another idiom for you.)

Answer

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.

*_*

Answer

when you've successfully played a trick on someone