A workgroup is a collection (usually nor more than 10) computers connected to each other via wired or wireless resources.  The computers are able to share resiurces such as printers and shared folders among the workgroup.

A domain relys upon a Domain controller (DC) to gain entry into this network and there is literally no limit to the numbers of objects (computers, printers, users, etc) the domain is allowed to hold within its boundaries.  Our current domain has more than 20,000 objects and is part of a larger domain numbering close to 400,000 objects.

Access to the domain is controlled to somewhat of an extent like a workgroup but is more complex and the DC has primary and secondary controllers for replication to handle all the task for authentication.  Your college will have itw own domain but I presume that will set aside one subnet of the local network for unauthenticated access, meaning you could use a workgroup computer from home on their netwrok, you just would not have access to the domain resources.

http://www.microsoft.com/windowsxp/using/networking/learnmore/russel_02april08.mspx

http://www.homenethelp.com/connection-sharing.asp

http://www.theeldergeek.com/quick_guide_to_simple_file_sharing.htm