*Black's d5 pawn is under attack by queen and knight. There is only 1 defender(Queen) and hence, played bishop( Bc8-> Be6). Thanks.
Why is this move Be6 a mistake or a blunder?
Sort:
I’m not sure but your King and Queen are rather exposed in this position. If white plays Nf3 forcing you to take, and takes back with his Queen, he can then discover check on the king AND attack the Queen with his bishop unless you use your 1 move correctly.
Thanks m3taphys 
.. Makes sense
My pleasure
Be6 is way too passive.
You should look for a more active defence, like Bb4.
The other benefit of Bb4 is you want to develop your kingside as fast as possible, so that you can finally get your king off that horrible f7 square on to the relatively safe g8 square, without permanently trapping your rook on h8 in the process.
Deranged wrote:
Be6 is way too passive.
You should look for a more active defence, like Bb4.
The other benefit of Bb4 is you want to develop your kingside as fast as possible, so that you can finally get your king off that horrible f7 square on to the relatively safe g8 square, without permanently trapping your rook on h8 in the process.
Yeah, urr that's what I meant to say...
I don't get HOW such a posirtion might have occured... it certainly needs some very weird moves being played,
Thanks for your suggestion Deranged
Yes Pfren, I did a mistake and inaccuracy in opening..And somehow managed to save piece but got king into open playground
This is what i did 
In the current set up, i played Be6,