Skewer
In chess, a skewer is an attack upon two pieces in a line and is similar to a pin.
A skewer is sometimes described as a "reverse pin."
The main difference is that in a skewer, the more valuable piece is the one under direct attack.
The opponent is needs to move the more valuable piece to avoid its capture, but this exposes the less valuable piece which can then be captured.
Only pieces that move in a line (bishops, rooks, and queens) can skewer. Kings, knights, and pawns cannot.
Answers
Re1
Bc4+
Re1+
Rd1+
Answers
Bg2
Be4
Bd4+
Bd4