In the context of cryptocurrency mining, a mining pool is the pooling of resources by miners, who share their processing power over a network, to split the reward equally, according to the amount of work they contributed to the probability of finding a block. A “share” is awarded to members of the mining pool who present a valid partial proof-of-work. Mining in pools began when the difficulty for mining increased to the point where it could take centuries for slower miners to generate a block. The solution to this problem was for miners to pool their resources so they could generate blocks more quickly and therefore receive a portion of the block reward on a consistent basis, rather than randomly once every few years.
Mining pools may contain hundreds or thousands of miners using specialized protocols. A pool can support “variable share difficulty” feature, which means that a miner can select the share target (the lower bound of share difficulty) on his own and change probability accordingly
Some Mining Pool protocols: Pay-per-Share, Proportional, Bitcoin Pooled mining, Pay-per-last-N-shares, Peer-to-Peer Mining Pool, Geometric method, Double Geometric method
Multipools switch between different altcoins and constantly calculate which coin is at that moment the most profitable to mine. Two key factors are involved in the algorithm that calculates profitability, the block time and the price on the exchanges. To avoid the need for many different wallets for all possible minable coins, multipools may automatically exchange the mined coin to a coin that is accepted in the mainstream (for example bitcoin). Using this method, because the most profitable coins are being mined and then sold for the intended coin, it is possible to receive more coins in the intended currency than by mining that currency alone. This method also increases demand on the intended coin, which has the side effect of increasing or stabilizing the value of the intended coin.