Mining-pool (Eng. mining pool) - is a union of miners who use their computer power together to increase the chances of mining the block and get an award for it.
The need for a bullet arises from the fact that as the hashrate grows, the complexity of the network increases, and the chances of block mining during solo mining tend to zero. Also, pools are the only opportunity for single miners to 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.