What Are "Shares" And How Do They Impact Mining?

[KillaStorm1000]

I've got CGMiner open and every 15-20 seconds or so it comes up with a share amount I got, the amount varies from 1 to 50~ normally, but my highest is 2,320. I would like to know what these shares are and what they have to do with mining.

[paul21]

A share is a unit of work (that's of difficulty listed in cgminer).

Basically each valid hash generated has to pass a difficulty test and when it passes the test, it is validated as a block and a payment is made. The way pools work is they divide this work for one block into shares that are of lesser difficulty. Each valid hash that passes the lower difficulty test is a share in finding a block because it might also pass a higher difficulty test (and find a block). It's a way of measuring contribution to the solution. Someone who gets close to the solution a lot will be given more shares and thus more of the block reward.

The share count also factors directly into how much you get paid. You get paid entirely on shares, the pool doesn't know your hash rate (other than guessing it by share rate).