Music is an art that moves through time. Some think music exists in space. And they're partially right since sound waves emanate into the air but ... as far as creating music goes, the composer works with time first and foremost.
A piece of music lasts a certain amount of time. Two minutes, twenty minutes, or an hour. It doesn't matter how long it lasts though. What matters is that the composer is aware of certain parameters. For instance, one of the first things you see when you look at sheet music is the time signature.
4/4 time and 3/4 time are 2 of the most common time signatures . It represents how many beats are in a measure and what note gets counted as the beat.