This site assumes that you know how to play chess—in other words, how the pieces move. If you know that much, you probably also know which pieces are worth more than which. But to be on the safe side, it is conventional to rank the pieces in the following order of value, with points given to them as indicated to make it easier to work out whether a set of exchanges is favorable or unfavorable:

Queen = 9

Rook = 5

Bishop = 3

Knight = 3

Pawn = 1