What is a Exchange Sacrifice ?

In my opinion an exchange sacrifice is one of the most fascinating parts of chess, it is not a mating combo or a sacrifice to get the material back in a few moves but a deep positional sacrifice that can change the character of the position. In my opinion a piece is not worth how much they say it is but what it is doing on the chess board. There are certain reasons why you should sacrifice a rook for a minor pieces and this is one of the reasons.                                                                                                  Attacking 

• To obtain the bishop pair (In a position where this element will play a major role)
• One dominant minor piece (A knight or a bishop in certain square where it can outplay the opponent’s rook)
• To destroy the opponent’s king shelter. (It is obvious that destroying the opponent’s castle is worth an exchange in most cases.)
• To damage the opponent’s pawn structure. (Sometimes, creating weak double pawns in the enemy’s camp compensates for the exchange)
• To win a central pawn (In many openings, like French Defense or Sicilian, it is common for black to sacrifice the exchange to win the d4 or e4 pawn.)                                                                                    Defence
• To block an open file (Sometimes, an exchange sacrifice can transform the pawn structure, bringing a pawn into an open file dominated by the opponent)
• To eliminate the attacking pieces of the opponent. (When being attacked, sacrificing a rook for the opponent’s active pieces is something that should be taken into consideration, it sometimes can even turn out to become a great counter-attack!)

These are some of the many examples when you should make a exchange sacrifice but remember it all depends on the position.