Rhythm is the organization of time in music: the steady beat underneath, and the patterns played against it.
The beat is the pulse you tap your foot to. Tempo is how fast that pulse goes, measured in beats per minute. Meter is how beats group: marches count in 2 or 4, waltzes in 3.
Melody tells you which notes; rhythm tells you when. The two are separable skills, and Tavi La Si trains them separately before music puts them back together.
Common questions
What is the difference between beat, tempo and meter?
The beat is the pulse itself, tempo is the speed of that pulse in beats per minute, and meter is how the beats group into bars of 2, 3 or 4.