A record chart (sometimes called a music chart) is a way of giving music a rank. The rank comes from the popularity of the music. The Billboard Hot 100 is a popular chart. The information on charts comes from some different sources, like the number of objects sold, the number of times a song was played on radio, the number of times a song or album was downloaded, and other criteria. Charts are sometimes made for a special genre, for example "Top 10 Rock Songs".