Blockade in general is one of the fundamental operations in chess. We will take the somewhat broader definition of Blockade as tactical element and distinguish three separate cases.
The first case is Blockade of the square. You cannot move your piece to a square that is already occupied by one of your pawns or pieces. We say that square is blocked. The most common use of tactical element Blockade is to force the opponent’s piece to a square that in return won’t be available for his other pieces.
A classic example is the game Alekhine-Houlsder, Amsterdam 1933.
White is ready to deliver checkmate along the h-file, but black king can escape to f7. That is why White must first blockade the f7 square! To achieve this White has to combine more tactical elements.
The other type of this tactical element is pawn Blockade. Pawn is blockaded if any piece stands on the square in front of it, regardless if it is his own or opponent’s piece.
Famous study by Alexey Troitsky from 1895. is a nice example.
Position after 4. Ke6. Both black pawns has been blockaded forcing Black to move his king. In this example, tactical elements Blockade and Zugzwang work together to bring victory.
The third case is Blockade of the piece. Blockaded piece is one that has no free squares. These squares are either occupied by pieces of the same color or controlled by enemy pieces. For example, in this case we will consider positions with trapped piece, as well as some trivial checkmates, e.g. checkmate along the first rank where the pawns blockade crucial squares to their own king.
Let’s look at another well-known study which is an example of employing the Blockade to checkmate the enemy king in the center of the board! Kakovin, 1936:
This is the final, checkmate position of the study. Black king is checkmated on while standing on a central square! Five squares are blockaded by his own pieces. Other three squares (including f4 pawn which delivers checkmate) are controlled by the white king and we can say that squares are blockaded by the white king.