It was originally developed as an auxiliary scoring method, but more recently it has been used as a tie-breaking system.
The method is to give each player a raw score of one point for each win and a half point for each draw.
When used for tie-breaking among players with the same raw score, no multiplying is necessary and the sum of the raw scores of the opponents played is used to break ties.
The major criticism of this system is that tie-break scores can be distorted by the set of opponents that each player plays (especially in early rounds).
To avoid this problem a version of Buchholz, the Median-Buchholz System is sometimes used.