Most music has a consistent grouping or pattern of beats.  These patterns of beats are referred to as "meters."  Groups of 2, 3, and 4 beats are the most common but others occur as well.  The groups of beats are called "measures."  The measures are separated by "barlines."

A meter with a grouping of 2 beats is referred to as a duple meter.
. . . 3 beats is triple meter
. . . 4 beats is quadruple meter

The different types of meters generally have different types of stresses on particular beats.  The chart below indicates the typical patterns.