In contrast with the client-server technology with which the web has made nearly everybody familiar, P2P technology connects the computers that run it together into a virtual network directly.
When a P2P file sharing program is running, whether or not you are actively downloading anything, you may also be also uploading files to other users of the software. In the case of Skype and other P2P internet telephony programs your computer may become part of a virtual telephone network through which calls between other parties are routed.
P2P software is often configured to run automatically when you switch your computer on, and most P2P software gives you little or no control over the extent to which your computer and your internet connection are exploited as part of its virtual network. It is certain that the College's fast internet connection attracts substantial amounts of through traffic to such programs running on computers connected to it; thus use of P2P software will almost inevitably slow your computer and your internet connection down.
To make matters worse, P2P filesharing is inherently insecure and is a common means by which viruses and other forms of malicious software are distributed.
The College prohibits all use of P2P software. It enforces this prohibition rigorously and many students have found themselves in trouble as a consequence.
The one exception to this rule is Skype. You can use Skype on the College network, as long as it is configured according to the instructions given here.