A discovered check flips the usual logic of checks: the piece that MOVES isn't the one giving check, the piece it uncovers is. That means the moving piece gets a completely free move, it can capture anything, land anywhere, even somewhere it could normally be taken, because the opponent is legally forced to answer the check first.
Nimzowitsch called the discovered check "the dagger in the back," and it's worth hunting for whenever one of your long-range pieces is lined up at the enemy king with exactly one of your own pieces in between. That blocking piece is a loaded spring.
White's bishop on c2 points straight at the king on h7, with only White's own knight on e4 in the way.
Move the knight anywhere you like. Where does it do the most damage?