In addition to staking XRD like other token holders, each validator node-runner may also receive emissions XRD tokens by specifying a validator fee. The validator fee is a % of the total emissions earned by stakers to the node, which is taken by the node-runner to incentivize their operation of a performant, reliable physical node.
XRD holders can see the % fee for each validator node by using the Radix Explorer website before choosing to stake.
Further reading: