Time Signatures
Time signatures organize rhythms in music. They state how many beats are in each bar and what type of note gets the beat. This type of organization helps musicians to stay on track while performing music.
We organize music into bars, also known as measures. The bars are separated by a barline which is line drawn down through the staff as seen here.
Each bar consists of the a number of beats which is determined by the time signature. Time signatures are made of two numbers. The top number states how many beats are in a bar and the bottom number tells us what kind of note gets the beat.
Time signatures can be divided in categories of Simple Meter, Compound Meter and Complex Meters. Simple meter is where the basic beat can be divided in 2's. Compound meter subdivides into 3's. Complex meters don't follow typical meters and may combine groups of 2' and 3's.
Here is a chart illustrating of some time signatures and what thier numbers mean.