Explanation

The moving piece discovers a check, but can also fulfill additional functions, as shown in the following examples:

Examples

Black can deliver discovered checkmate with Bf4#.
The bishop on f4 prevents White from blocking the check with Rh4.

Black can deliver discovered checkmate with Re6#.
The rook on e6 protects the knight on e3, preventing White from defending with Kxe3. The proctected knight also guards the escape squares g4 and f5.

White can deliver discovered checkmate with Bxf4#.
The bishop captures the knight on f4, and prevents Black from defending with Nxh3.

Pattern matching

Discovered checks can be very dangerous, because the piece discovering the check can go to any square without fearing to be captured. Apart from winning material, that move can also be used to interfere with the possible defences against the check.

Related patterns

In discovered check, you win material with the discovered check.
In double check mate, the king is checkmated by two pieces simultaneously.