There are different systems to giving point values to chess pieces. These values help determine how valuable a piece is strategically. They play no formal role in the game but are useful to players when assessing a piece's relative strength in potential exchanges.
For example: Sacrificing one's rook for a bishop might not be a worthwhile exchange, as a bishop is a more valuable piece.
Note! Calculations of the value of pieces provide only a rough idea of the state of play. The exact piece values will depend on the game situation, and can differ considerably from those given here. In some positions, a well-placed piece might be much more valuable than indicated this chart, while a badly placed piece may be completely trapped and, thus, almost worthless.