Musical notation is a system that uses written symbols to visually represent music that is heard. It includes staff lines where music is written, as well as different types of bar lines that divide music into measures and sections or indicate repeats. The staff consists of five lines and four spaces that are numbered from bottom to top. There are single bar lines that separate measures, double bar lines that separate sections, an end double bar line to indicate the end of a piece, and a repeat symbol to show a section should be repeated.