What is this opening called on black side

g6 Bg7 Nf6 0-0 and these next moves are done if there is the ability to do so safely.  If there is no advantage then they can be altered or traded for better move more suited to your situation.  e5 d6

Well, you can't castle on move 3, as your bishop is still in the way. Assuming you mean...

1. g6 2. Bg7 3. Nf6 4. 0-0, then that would be the Modern Defense.

that's what i put.

that's not a very good opening and cannot always be used (Depending on what white plays) . It's commonly a response to E5 but if you're going to play that then instead play Sicilian.

I thought it was a response to 1. d4 Nf6 2. c4

In the case of it being in response to d4, it is generally a King's Indian Defense...the Modern plays without Nf6.

I saw casperov use it.  Or carpov.  um...  It's worked for me.  so far.

You mean Casper the Friendly Ghost?

It's a modern until move #3, when it transposes to either a Pirc or a King's Indian, depending on what white has played.

And the Pirc coordinates are what?  Just curious.

so what it's called is simply based on what white plays?  Maybe i should read my book.  It's been about six years since i've actually read a chess book and I guess i thought more of my opening knowledge than i actually do.  So to the books.  Thanks