Repeats in music allow you so not have to write the same section of music multiple times. It allows the musician to simply memorize one section and rather than turn a page or continue reading, simply follow the repeat.
It looks like a bar line with two dots next to it. There are 2 repeats: the beginning and the end. The result is that you repeat the section of music that is within both repeats bars.
There are also things like CODA’s which I’ll discus in the near future.