In Polkadot staking, validators are identified as either Relaychain validators or Para Validators.
This appears to mean that a validator has is started with arguments that allow it to validate (randomly selected?) parachain blocks. Still, I cannot find that argument in the options to run a Polkadot node.
So what is the difference between the two types of validators?
I may be looking at this the wrong way around. Perhaps it is a collator from a Parachain that has its Polkadot startup arguments set to validate on the Polkadot chain as well - in which case, I could see how this could be both a Relaychain Validator and a Parachain Collator at the same time. Is this the answer?