For a general overview about staking, please navigate here.
Each validator has its own unique commission which reflects a percentage of all staking rewards that are set aside to help cover costs for running those validators and securing the Kujira network.
As an example of how commission might work, say a validator has a 5% commission, has 1 million KUJI in total delegations, and that Kuijra has a 1 year forward looking APR of 10%. On the Kujira chain, as you may know, staking rewards are paid out in the tokens actually used on the chain (though they may also be converted to KUJI when withdrawing). As an approximate measure of a calculation for that validator's total revenue. They would obtain 1 million KUJI * 10% rewards * 5% commission = 5000 KUJI per year in revenue assuming those conditions stayed constant.
Say that we revisit this same scenario above and that you are a delegator to this validator with 1000 KUJI staked. In a year, you would obtain 1000 KUJI * 10% rewards *95% not taken as commission = 95 KUJI.
In general, the lower the commission the greater the portion of staking rewards you collect by staking with a validator. The higher the commission, the more funding that you are providing directly to an entity that you are staking with. However, this is only one aspect of choosing a validator. It is also very important to consider a validator's technical expertise. As mentioned here, if a validator gets slashed, you will lose a portion of your tokens delegated to the validator. Validators may also contribute to the chain in other ways to stand out (something that we always encourage).