I got an XBOX 360 4G for Christmas, ordered a 250GB drive from e-bay 1st week of January. It is simple to install, simply open the door and slide it in. Been working perfectly. There was some configuration to do but the XBOX walks you through it when it recognizes the new hard drive.
Ok so I dont know the exact terminology but only trying to tell OP for basic game play of grade school aged children it stores the progress of their game play .