Mining hardware includes all equipment such as CPUs, GPUs, FPGAs, and ASICs that can be used effectively to calculate hashes for mining Bitcoin. This also covers the production, and producers of such equipment.
Mining cryptocurrencies requires hardware to perform the Proof of Work calculation. These calculations can be done with a general purpose CPU. They can often be done with a GPU in order to obtain a higher hash rate. Some mining algorithms can be programmed into Field Programmable Gate Arrays (FPGAs) and even into hardware circuitry itself for more efficiency and a higher hash rate.