Clearance for pin (3 moves)
Master this and many more motifs
Clearance is similar to a discovered attack or discovered check, in that you move one piece to reveal a threat of another piece. For a discovered attack or check that threat is a direct attack or check. For clearance, that threat can be checkmate, or some other tactics.
A clearing move can be especially strong if it is a forcing move, for example a capture, a check, or an attack. In that case, the opponent often cannot handle that forcing move, and the revealed threat at the same time.
In this level the revealed threat is a pin. You move one piece out of the way for another piece to pin and win on a subsequent move.
Black can play d5 to attack White's bishop on c4, and clear the way for the bishop to c5.
If White captures with exd5, or retreats the bishop, Black can pin White's queen to the king with Bc5.
Otherwise White loses the bishop.
Sometimes the clearing move can include other motifs:
White can give a discovered check with d6+.
The pawn reveals the check from White's queen and also attacks Black's queen.
Black can deal with both threats with Qf7, however the pawn has also cleared the way for White's bishop to d5.
White can now pin the queen with Bd5.
With clearance, you move one piece to reveal a threat of another piece.
If that threat is a direct attack, it is called discovered attack, or discovered check.
You can also combine clearance with other motifs: