When you digitize something, you adapt it into a form that can be read by a computer. Publishers digitize books so they can be read on e-readers, tablets, and smartphones.
You can digitize your parents' old photographs by scanning them and then uploading them. And since record companies started to digitize music, that's increasingly how people listen to it — while you may enjoy playing records on an old turntable, you probably listen to new music using an app on your phone or computer. Since 1953, this verb has been used to mean "convert into a sequence of digits," specifically digits a computer can read.