How validators are chosen
The network picks validators to propose blocks, usually in proportion to the amount they have staked. Other validators vote to confirm each block. Because no mining is involved, proof of stake uses a tiny fraction of the energy of proof of work.
Slashing and risks
A validator that signs conflicting blocks or tries to cheat can be slashed, meaning part of its stake is destroyed. Critics worry that large holders and big staking providers gain outsized influence over the network.