An MP3 is a kind of file used for sending music or other material over the Internet. These files are compressed, or reduced in size, compared to songs on a compact disc, or CD. MP3 files are played on a computer using media programs. MP3s can also be played on small players as well as some wireless telephones that can store music. Many players can hold thousands of songs yet are small enough to carry in your pocket. Music fans can change their music collections from CDs to MP3s. They are also able to download MP3 music files from the Internet much faster because of the MP3's smaller file size. File-sharing services make it possible for people to exchange copyrighted music at no cost. However, the record industry starts to get concerned because people are trading free music on the Internet instead of buying it in music stores.