Double check

Start of chess board.
a8 __ b8 __ c8 __ d8 __ e8 __ f8 __ g8 black king h8 __
a7 __ b7 __ c7 __ d7 __ e7 __ f7 __ g7 __ h7 __
a6 __ b6 __ c6 __ d6 __ e6 __ f6 __ g6 __ h6 __
a5 __ b5 __ c5 __ d5 __ e5 __ f5 __ g5 __ h5 __
a4 __ b4 __ c4 __ d4 __ e4 __ f4 __ g4 white bishop h4 __
a3 __ b3 __ c3 __ d3 __ e3 __ f3 __ g3 __ h3 __
a2 __ b2 __ c2 __ d2 __ e2 __ f2 __ g2 white rook h2 __
a1 __ b1 __ c1 __ d1 __ e1 __ f1 __ g1 white king h1 __
End of chess board.
Be6++ is double check

Double check is a chess term. It describes when the king is being attacked from two places at once. This forces the king to move, because taking one attacker or blocking one attacker will not solve the problem from the other attacker.