A mining pool is an association of miners that combine their computing resources to mine cryptocurrency blocks and split the reward equally, according to the contributed amount of work. Mining pools became necessary when the difficulty of proof-of-work cryptocurrency mining increased so much that it became impossible for the average miner to mine a full block. The growing difficulty led to the establishment of the first mining pools for Bitcoin. Today, Bitcoin mining pools are the most influential communities in the Bitcoin network and are the major organs that decide whether new forks should be implemented. There are also Ethereum mining pools, Litecoin mining pools and mining pools of other major cryptocurrencies that are too hard to mine alone. There are also mining multipools that switch from one cryptocurrency to another when it becomes more profitable to mine.