Proof of work is a collective agreement mechanism. In this mechanism, each node participates in the process of verifying and mining based on the amount of their processing resources (like Bitcoin). The basis of this cooperation is performing extremely hard calculations for finding a mathematical solution (finding the intended hash) and any node who can solve this problem quicker and find the result, have a chance to add his/her block to the end of the chain and if the block is accepted by the network, receive the reward for mining a block.