An example of a compound meter could be 3/4 : 2/4. After every measure you change meter. The first measure would be in 3/4. The second in 2/4, then back to 3/4 and so on. A compound meter has a compound time signature with more than one type of meter. You could have a pattern of several time signatures one after another. Each measure would be in a different time signature based on the sequence. At some point it becomes easier to read when the meter changes are written in. But if you have a pattern of only two or three meters, it simplifies the notation to use a compound meter.