Socket - typically tells you the kind of processor it supports. It has a certain number of pins.
That is why you can never upgrade a motherboard/processor alone, due to the sockets.
If you choose to upgrade individually, you have to do a lot of research.
Go to the motherboard manufacturer's website and check out what type of processors is supported or what type of socket is supported by a particular motherboard model.
Another website to go is
http://www.motherboards.org/. You select the type of socket and it will give you a list of motherboard using that socket and vice versa.
Socket F is just another type of socket supporting certain processors, specifically, the AMD Opteron processors.