Playing MP3's on Ipod

Hello,
I do not have an Ipod myself,but both my brother and niece have the 20 or 30 GB size. I'm sure playing MP3's on them would be no problem, if we could figure out how to do it.

They keep asking me like I would know this, but they both have MP3 files on a cd and want to play these files on their ipod.

Do they have to first convert them from MP3 to .aa or whatever files Apple uses as their default playing file?
Or do they convert on the fly when you put them into the library. The easiest explanation if possible would be greatly appreciated. Thank you so much!

copy the cd onto the computer where their music is stored

use itunes to rescan for music files

they should be available to upload to their ipods now

if you let IPOD rip the CD then you won't be able to use windows media player to play them on your computer ... they will only be playable through the IPOD software ... I would suggest using another program to rip the tracks from the cd, you can then load them into your IPOD ... and at the same time you will have them in a folder where they are MP3's and you will be able to play them on the comp through windows media player ... my husband spent days ripping all his cd's through the IPOD software, and when he went to play them with windows media player they were all in a format that it didn't recognize ...