Pai download (also known as a digital download or a digital single) is an official and legal music single available for purchase through an online store. Popular examples of online music stores that sell digital singles and albums include the iTunes Store and Napster. Not only is digital downloading for music there are also audio books and travel guides which can be found at sight such as Lodingo and Audible. Downloads are often encoded with Digital Rights Management that restricts making extra copies of the music or play purchased songs on certain digital audio players.