iTunes is an audio playback program developed by Apple Computer. You can use iTunes to import songs from CDs as well as other audio files from your hard drive. The program can also download songs (for a small fee) from the iTunes Music Store. While songs are the most common files played by iTunes, you can also play spoken word files, such as audio books or other recordings. iTunes also has a radio option that allows you to play live streams of Internet radio from a variety of stations.
Each file you import with iTunes get stored in the iTunes library. Fortunately, the library can be organized into multiple playlists, which is especially helpful when you have thousands of songs. (Yes, some people have over 10,000 songs in their library.) You can also create "smart playlists," which store songs according to the parameters you set. For example, if you want a playlist of only rock music, you can create a smart playlist that only holds songs where the "Genre" tag contains "Rock." iTunes is the software that comes with the iPod, and allows you to transfer your playlists from your computer to your iPod. Like the iPod, iTunes can be used on a Mac or PC.