For the younger folks: Napster arose when CDs and radio were the dominant official commercial distribution platforms for music. CD ripping into MP3s and portable music players drove the need to share them, and the internet was new, but needed a more scalable way to exchange them. Back in the day, it was mostly IRC channels, but these were slow and cumbersome. So Napster, Gnutella, and Hotline took off. These gradually gave way to eDonkey2000/eMule, KaZaA, and Limewire. These also then gave way to BitTorrent and overlay p2p apps.