Mining pool (English mining pool) is an association miners who share their computer power to increase the chances of getting a block and get a reward for it.
The Need in the pool arises due to the fact that as the hashrate increases
the complexity of the network, and the chances of mining the block during solo mining tend to to zero. Also pools are the only possibility for single miners. Compete with large mining farms that build large
companies for millions of dollars.
The income from mining in the pool is divided between the participants in proportion to their allocated power. It is also worth considering that each pool sets its commission for the work and takes part of the profits.
In the context of cryptocurrency mining, a mining pool is a pool of miner resources that divide their computing power across the network to distribute the reward equally based on the amount of work they contributed to the probability of block detection. The “share” is awarded to members of the mining group who present actual partial proof of work.
Mining in pools began when the complexity of mining increased to such an extent that slow miners could take centuries to create a block. The solution to this problem was for miners to pool their resources so that they could generate blocks faster and, therefore, receive part of the reward for the block on a consistent basis rather than randomly every few years. ( Wiki )