Back in the long long ago, music was kept on these limited storage capacity devices called records, which were replaced by cassettes, which were replaced by CDs. The main problem of these ancient contraptions was they could only hold a few songs at a time. To listen to something else, you had to PHYSICALLY SWITCH to a different one. With the advent of the MP3, came the MP3 Player. Suddenly, you could hold 100s then 1000s then 10000s of songs. All on one tiny little box.