As part of bitcoin mining, mining “pools” are a network of miners that work together to mine a block, then split the block reward among the pool miners. Mining pools are a good way for miners to combine their resources to increase the probability of mining a block, and also contribute to the overall health and decentralization of the bitcoin network.
A collection of mining clients which collectively mine a block and then split the reward between them. Mining pools are a useful means to increase the probability of successful mining a block as difficulty rises. As the amount of computing power needed to mine a block has risen, those who do not have the resources or skills needed to compete can merge their computing power with others and get a proportional return on blocks discovered. The rise in pools has also given rise to concentrations of hashing power, leading to concerns of a 51% attack . So far, in practice, miners have been careful not too violate this limit to protect the integrity of the system and to maintain the value of their holdings.
Malone, J.A (2015). Glossary of Bitcoin Terms and Definitions. United States: Lulu Press, Inc