Unravelling the mysteries of Rhythm: Rhythm is nothing more than how musical stuff is spaced in time. The two things you need are some musical events (some notes, hand claps, strumming strings, whatever) and some time in between them. Thats it.
Music is far easier than many people think. One way of seeing it is like Legos®. With a few simple building blocks, you can make simple objects, or more complicated ones. With a variety of additional kinds of blocks, you can make immensely complex constructions. That is actually how it is with music, and this article explains how the Strumstick demonstrates that.