We begin with discoveries where the bishop unmasks an attack by a queen or rook running up or down the board or from side to side. The position on the left is a skeletal illustration. If White moves his bishop to c4, it checks Black’s king; the bishop’s move also unmasks, or “discovers,” an attack by the White rook on Black’s queen, which White will win next move. The job of the piece in front is to give check and thus keep your opponent busy; the piece in the rear then has its chance to carry out a capture. This is the typical pattern, though there are others we will study later.
Before a discovered attack is unleashed there always are three pieces in a line on a rank, file, or diagonal: the masked piece, the piece about to unmask it, and the target. When the bishop is doing the unmasking, the three pieces always are on a file or a rank. That is the kernel to look for in the positions that follow: a bishop blocking the path of a rook or queen. Then we'll follow up with standard questions: whether the two pieces in the kernel both have good targets, or whether targets might be created for them; whether the needed lines are clear or can be cleared; etc.
We also can work toward discovered attacks by thinking about the suitable targets for them. Bishop discoveries always unmask attacks by queens and rooks. It follows that the target of the unmasked piece usually needs to be a queen or a loose piece for the attack to turn a profit. Unmasking an attack by your rook against a protected bishop, for example, isn't going to scare your opponent; the rook's target needs to be a loose piece or else a protected piece that is more valuable, such as the enemy queen (whether it's guarded or not).
But now we're getting a little ahead of our story. Let’s start by studying some positions involving discoveries by the bishop in simplest form.