That means you can save up to 40 minutes of MP3 audio onto the player and take it wherever you go. On Removable Media You could also save MP3 files onto various removable discs and media cards. Disks, most removable media are solid state and do not have to be read by a disc drive. However, there are tons of sites that violate copyrights. Because of all of the attention MP3 is getting in the media, many big name MP3 sites are complying to the rules and only posting legal stuff.
Some players come USB only.
There are number of different places online that you may download legal MP3 files from. Your best bet is to go to your favorite search engine and type MP3. But on average, one minute of MP3 audio needs 1MB to store. So if you have a portable MP3 player with a 40MB internal memory and place for a 40MB media card, you can take with you about 80 minutes of MP3 music. Most MP3 players run on regular AA or AAA batteries.