How does Proof of Staking protocol actually works?

I understood that PoS works by randomly selecting nodes, with respect to amount of coins staked. That node has to verify the block and this process can make PoS more decentralized, fast and cheaper. But how do they still "verify" the block? Kindly explain.

Like incase of PoW, they use superfast computers to guess the hash of a block, something like that, do they still need superfast computer resources in PoS? Or what protocol they use?