Application-Specific Integrated Circuit (ASIC)
An Application-Specific Integrated Circuit (ASIC) is a special microchip built for exactly one purpose. Bitcoin ASIC miners, the hardware devices that contain these chips, are designed solely to hash blocks in order to find a valid Proof-of-Work.
Because mining has become such a large industry, the difficulty has risen to the point where using a CPU or GPU to mine is no longer profitable. Having a single purpose affords ASIC miners critical efficiency gains in an industry where the tiniest efficiency improvement can give a miner the edge. The rapid innovation around Bitcoin ASICs has partially driven the explosion of hash rate over the last decade, bolstering Bitcoin’s security.