A count — or a “beat” (either term will work) — is a certain amount of time, constantly “ticking by” in a piece of music (such as a song). It can change, but not often. It is determined by the tempo of the piece. If the tempo is fast, the counts will go by quickly and last shorter. If the tempo is slow, the counts will go by slowly and last longer. Counts are also “assigned” to a certain note-length (described in more detail later), such as “4-4 time,” which means that a quarter-note is assigned one count/beat.