They are file sharing programs that allow folks to connect to other computers and share with them - primarily music files. There are so many viruses passed along via these programs (mainly embedded in the shared files) that it is a wonder folks still use them.
Thanks.
May Thanks.
People go on and on about viruses magically appearing on their computer from some internet-type software (it ranges from IE to Winmx to Instant Messenger), but honestly, unless you're doing something stupid (like actually allowing people to just put things on your computer), there is no way to just magically get a virus from any of these kinds of software.
Sorry for going off there, but people's fear of the unknown and viruses just gets old to me.