Answer:
An FPGA is a field programmable gate array. It could be "programmed" to do certain task, but don't mistake it with a microprocessor. When programming an FPGA, you're actually changing it's physical structure, the logic gates inside the FPGA, to do the task for you. Therefore, unlike a microprocessor which has to run through a series of command, an FPGA could be rewired to run at a much faster and more efficient rate.
FPGA is good for testbenching and are budget friendly since they can be reprogrammed over and over again in case you messed up. However, they can be quite big and bulky, so they are not suitable for mass production.
ASIC in the other hand can be compact to a small size. ASIC are pretty much the IC chips that you use, like your Intel CPU or LM7000 series chips. However, the process of making them that small is irreversible, so if you messed up, you gotta throw away the whole batch. This make them expensive to make, but their small size and production process allows them to be made in bulk.
Both FPGA and ASIC are good for power consumption and speed because you're actually designing their physical circuit layout, so if your design is efficient then the product will be efficient in both speed and power as well.
In Summary, you design and test your circuit using an FPGA first. Then you send that design to a production company and they will use that design to mass produce it as a small chip.
