Chapter 1 of 5 · Meet the idea
Count the whole shopping bill.
Come out of the exchange with more useful fighting power. The whole sequence matters more than the first capture.
Material means the pieces and pawns available to fight. Approximate values—1 for a pawn, 3 for a knight or bishop, 5 for a rook and 9 for a queen—help compare exchanges. Count what both sides lose, not just the first piece you take.