An economical mate is when a checkmate is achieved using all the remaining knights, bishops, rooks, and queens of the attacker in the attack. The attacker’s pawns and king may also participate in the mate, but their contribution is optional and doesn’t affect whether the position is considered an economical mate or not.
Chess composers are drawn to economical mates due to their aesthetic appeal, but they rarely occur in actual gameplay. Despite their infrequency, some memorable games have ended with an economical mate, including Paul Morphy‘s famous Opera game.
By the way, when I say “they rarely occur”, I mean a position with more than one piece left on the board. In fact, an “economical” mate given by the queen and king against a king is pretty common in games of beginners, as less experienced players usually play until the bitter end.
Let’s see, as a great example, the following game. I will skip the analysis of most moves, and focus on the final position: