Meter is the regularly recurring grouping of stressed and unstressed beats into measures. In Western music notation the meter of a piece is indicated by its time signature, also sometimes called a 'meter signature,' which is placed at the piece's beginning as well as at the start of any change in meter.
The most common meter is quadruple meter, which is used extensively in both classical music and popular music and is used almost exclusively in marches. It has a time signature of 4/4, which means that there are four beats per measure, with a pattern of strong, weak, medium, weakest, and with each beat being one quarter note. Quadruple meter is also referred to as common time, and is frequently indicated by the letter 'C.' 3/4 time meter, used mostly in waltzes and some other classical genres, has three quarter-note beats per measure, with the accent usually on the first beat. A somewhat less common meter is 6/8, which is an example of a compound meter.