iTunes can create playlists of certain types of music, songs with certain ratings, or songs that match other rules you specify. iTunes can update these playlists automatically.
For example, you could create a Smart Playlist that’s no more than 5 gigabytes (GB) in size and includes your most highly rated jazz songs. Or you could create a Smart Playlist of songs by a particular artist. When you import a new CD from that artist, the songs are added automatically to the Smart Playlist.
A Smart Playlist has this icon next to it. iTunes comes with several Smart Playlists already set up, including My Top Rated, Recently Added, and Top 25 Most Played.
To create a Smart Playlist:
Choose File > New Smart Playlist.
Specify your rules.
To change a Smart Playlist, select it and choose File > Edit Smart Playlist.
To remove a Smart Playlist, select it in a list on the left side of the iTunes window and press the Delete key.