Discovered check 1
A discovered check is really an uncovered check.
In diagram1 the black king is not in check from the white rook because the
white bishop is in the way. Suppose white plays Bb5 as in diagram 2
Diagram 1 Diagram 2
The bishop has now moved away. The path from the rook to the black king has
been uncovered. This is called a discovered check.
In diagram 3 we see that the white bishop can be used to attack the black
queen.
