Meter is the grouping of beat patterns. Certain beats are stressed more than others in music and this causes the beats to fall into perceptible patterns. These patterns almost always come in twos or threes.
Fundamental Meter Groupings:
These meters are the most basic meters. Almost all of the other meters are some combination of these two.
Duple: [1 - 2], [1 - 2], [1 - 2], [1 - 2], etc.