I know that a peer in a cryptocurrency network can contribute deciding the next block that has to be added to the blockchain. To do that and gain some rewards, such peer has to be the first peer able to resolve some PoW algorithm. From what I have understood, mining pools use computational power of client machines in order to resolve the PoW as fast as possible. I guess so that the mining pool server is the only peer that directly participates to the network and it performs entirely the algorithm using the computational power of the clients which perform only some secondary tasks.
How can be splitted this computational task to many clients?