Priority fees
A priority fee is an optional extra fee someone adds to a Solana transaction to get it processed sooner, on top of the small base fee every transaction pays. Priority fees go to the validator that produces the block. Whether any of that money reaches the validator's stakers is up to the validator.
Why it matters to you
Priority fees are part of what your stake helps a validator earn. Solana assigns block-producing turns based on stake, so the more SOL delegated to a validator, the more blocks it gets to produce and the more priority fees it collects.
By default, those fees stay with the validator. Your rewards come from inflation (new SOL the network issues) and, if the validator runs Jito, from MEV tips (extra income from ordering transactions). Priority fees reach you only if the validator decides to share them.
That doesn't make keeping them wrong. It does mean the commission percentage alone doesn't show everything a validator earns from your stake.
Where you see it on this site
On validator pages and in the list, the fees card shows the two commissions taken from your rewards, as "rewards / MEV". Priority fees aren't part of either number: they are income the validator collects directly.
Questions
Not automatically. Priority fees go to the validator that produces the block, and the validator keeps them unless it chooses to share. Your regular staking rewards come from inflation and, with validators that run Jito, from MEV tips. Any priority-fee sharing is a separate choice each validator makes.