Beatmatching is one of the most fundamental and important concepts in DJing. It basically means matching the downbeats of two concurrently playing tracks such that they are playing on top of one another. This typically involves temporarily speeding up or slowing down one or both tracks and/or changing their tempos such that their beats align.

Beatmatching is what allows DJs to seamlessly mix one track to the next such that it all sounds like one continuous track.