What is FPGA?

I have been hearing FPGA at work several times and I come into a decision to make it a point to study exactly what is FPGA.

According to Wikipedia, FPGA is

"A field-programmable gate array is a semiconductor device containing programmable logic components called "logic blocks", and programmable interconnects. Logic blocks can be programmed to perform the function of basic logic gates such as AND, and XOR, or more complex combinational functions such as decoders or mathematical functions. In most FPGAs, the logic blocks also include memory elements, which may be simple flip-flops or more complete blocks of memory."

Field-programmable gate array (FPGA)
http://en.wikipedia.org/wiki/Field-programmable_gate_array