I never heard of "open check"?
open check
if king is in e1 and pawn is in d2 and opponent bishop in a5,
and if pawn moves to d3, opponent bishop can take away king. In this case what is this situation called? Is this pawn's move valid?

if king is in e1 and pawn is in d2 and opponent bishop in a5,
and if pawn moves to d3, opponent bishop can take away king. In this case what is this situation called? Is this pawn's move valid?
You can't move into check, so the d2 pawn can't move in that situation.
1) what is open check in chess?
2) Is it possible to do open check and loose the game?