ways to use them .programming.i've only just heard they exist .
Ah, we'll the most common ways of writing code for FPGAs are in the form of an HDL; most commonly Verilog or VHDL. Programming/debugging is typically done via JTAG.
If you're not familiar with what an FPGA actually is, I'd recommend doing a Google search on it. In short, they are arrays of LUT's connected by programmable interconnects. Microprocessors contain a few functions (mnemonics) that can be used in succession to achieve a certain task, and FPGA's can do everything in a single clock cycle because you define the logic in hardware (you can create your own instruction set).