As we learned in the Dividing the Beat lesson, there are two main parts to any meter, the beat and the subdivision of the beat. The beat is what we tap our foot to, or nod our head to when we listen to music. Subdivisions are the faster moving, more complex musical rhythms created by breaking up our beats into smaller parts. Up to this point we have only dealt with simple meters. Simple meters always divide their beats into subdivisions of two equal parts, which we learned to count "one and two and three and four and." Those two equal parts can continue to be divided into ever smaller durations to create subdivisions of four, or eight, or sixteen, etc. Below is an example of a simple meter (4/4 - quadruple simple), first showing quarter-note beats, then showing those beats subdivided in twos (in this case eighth notes) and then subdivided in fours (in this case sixteenth notes, which we typically count "one-e-and-uh, two-e-and-uh, three-e-and-uh, four-e-and-uh"). 

We can get an enormous amount of rhythmic variety out of music in simple meter, but there is something clearly missing here: being able to divide the beats into three equal parts. That brings us to compound meters, which are meters that subdivide into three parts rather than two.