BPM stands for beats per minute and refers to the number of beats (or crotchets, or quarter notes) that occur in a minute of time for a given piece of music. BPM is a measurement of tempo. The importance of BPMs is demonstrated when beat matching, which is a style of mixing. This style is based on the concept of having 2 different songs with two different BPMs that are not perfectly matched with one another. The goal is to get the two songs to match by either increasing or decreasing the speed of one or both songs, until their BPMs level out and match one another.