For this reason, the piano is related to the percussion family. Most Western music is written so that one beat out of every few is accented. The meter usually reads with one number on top, and one on the bottom. The bottom refers to the kind of note that gets a beat. When you count the beat of a song, you can usually feel the first beat accented.
Waltzes usually are in three time.
Rhythm is a pattern you make in between the beats. Usually people tap the beat of a song with their feet. You can also clap or speak different rhythms within that beat. They are saying a rhythm within a regular beat. Try experimenting with saying different rhythms as your feet tap the same consistent beat.