A GPU miner is a computer program that uses a graphics processing unit (GPU) to mine cryptocurrency. GPU mining is more efficient than CPU mining, as a GPU has many more cores and is specifically designed for parallel processing. GPU miners can be used to mine a variety of cryptocurrencies, such as Bitcoin, Litecoin, and Ethereum. They are often used in conjunction with mining pools, which allow miners to combine their resources to increase their chances of finding a block and earning rewards.