What Is a ‘Share’ in the Context of Cryptocurrency Mining?

A 'share' is a proof-of-work submitted by a miner to the pool that meets the pool's set difficulty target, which is lower than the network's target. It signifies that the miner has done a measurable amount of computational work.

Shares are used as accounting units to calculate each miner's contribution to the pool's effort. A large number of shares is required to eventually find a valid block that meets the high network difficulty.