A validator can get rewards by executing transactions. Each transaction has an execution cost and
of this cost goes to the validator, but
of the reward goes to the system treasury that can use these funds for the system needs, such as bridging cost coverage and relaying. Not all block rewards go to the validator's owner. A share of them is also distributed between delegators.
Whenever the validator's owner creates a new validator, the commission rate must be specified. The commission rate defines what percentage of the block reward goes to the validator owner. It is limited to 0% up to 30% to limit validators from setting very high commission rates.
On the other hand, delegators' rewards are also calculated based on their total staked amount at the validator. The reward is calculated per one validator. The total rewards for a delegator, if staked at different validators, is the sum or per-validator rewards.