Mac266 :
I don't get it. So they make PGA sockets/CPU's? And here I thought Intel were full LGA now...
FPGA in this context has nothing to do with sockets. It stands for "Field-Programmable Gate Array" which is a form of programmable logic often used for rapid-prototyping, signal processing, network routers/switches and other applications that require very fast, low-latency processing but either lack the production volume to justify a custom ASIC or where devices must be field-upgradable/customizable.
If you design a switch or router around an ASIC chipset, you have to make every future feature fit within the functions baked into your ASICs. If you use FPGAs, you can make the router or switch do whatever you want whenever you want, as long as the logic design still fits inside available FPGAs and connected resources.
FPGAs are at the boundary between software and hardware engineering.