Well, GPRS stands for General Packet Radio Service. It's simply a way maintaining a constant connection to the internet I think. Regarding requirements of a mobile phone to send/receive mms and video mms, I'd say that GPRS is pretty necessary (or at least an internet conection), along with software (and a powerful enough processor) that tells the phone what to send, how to send it, and where it needs to go!
And you'll need to make sure that your provider has it enabled on your account - not as easy as it sounds if you are with the one named after a fruit, took me four calls to customer services before they finally sorted it out!
Good point Hammer - had a similarly fruity experience! Think they have it a bit more sorted now as it used to be case that you couldn't send mms cross network, but that's fixed now!
Essentially that would be called "data-transfer" - depending on the phone, you could send it using either infrared, bluetooth, or wifi. Hope that helps!