Repeat sign. What's that?

In music, a repeat sign (see above image) is a sign that indicates a section should be repeated. If the piece has one repeat sign alone, then that means to repeat from the beginning, and then continue on (or stop, if the sign appears at the end of the piece).

A corresponding sign (see far left of image below) facing the other way indicates where the repeat is to begin. 

When a repeat calls for a different ending, numbered brackets above the bars indicate which to play the first time (1.), which to play the second time (2.), and so on if necessary. These are called "first-time bars" and "second-time bars", or "first and second endings".

If you have any questions, feel free to comment below.