Why is e6 better than e5 in this opening?

Black moves e5 and Stockfish 12 tells me that e6 is the better move. Why is that?

Would that not block in the white square bishop?

Sorry if this is the wrong section - it is my first time posting on the forums.

When you say "better".  How much of a difference are we talking?  If its something ridiculously low like .1 it doesn't matter. 

IMKeto is right. The difference is within .1 pawns for the computer evaluation. Playing e5 is definitely the more natural move, and what most players would play in that position. Something that small in the evaluation either means nothing because once it gets to the position that it evaluates that slight advantage position will probably have the same evaluation (as far as outlook of the overall result of the position) that playing e5 would have, or the advantage is like 30 moves down the best line to make a difference which no human is able to do. 

Thank you both for the response.

Below Master-level, no one ever loses because they choose moves that are 0.2 "worse" than the best move possible.  It's the big blunders, or failing to take advantage of your opponent's big blunders, that decide games.

+1 

The OP is rated 700. Small inaccuracies do not matter at that level. 

It could be because both pawns are more vulnerable to attack, as an e5 pawn push means that the d5 pawn can no longer be defended by another pawn unless Black plays ...d4. White has a really passive position, so I don't really see it as an immediate problem, but White could eventually fianchetto his bishop on g2 and develop his knight on e2 and keep d4 protected, while trying to keep his bishop fixated on d5. At some point, Black will have to play e4 to cover the d5 weakness, which might not be a big deal, considering Black's space advantage. But it's more of a positional consideration, and in a blitz/rapid game, I'd be very comfortable playing ...e5 as Black, too.