2.Material

When a player is up in material, there is a saying "exchange all the pieces". The reasoning behind this is that once you exchange all the pieces, you will stay with the extra material. By itself, being material up can mean different pieces, but the smallest unit is a pawn, that can also be promoted later on if the pieces are exchanged. With too many pieces on the board, being up in material may not be too relevant since there is plenty of battle left, but with reduced material, the extra material will come to light. If possible, we would like to exchange pieces by not allowing any counterplay from the opponent, and that's another thing to note if the scenario is reversed - if we are down in material, usually we would like to avoid exchanges.