How does the Ethereum PoS consensus mechanism work after The Merge?

After The Merge (September 15, 2022), Ethereum uses Casper FFG + LMD-GHOST consensus (collectively called Gasper). How it works: (1) Validators — must stake 32 ETH to participate. ~1 million validators as of 2024; (2) Epochs and slots — time is divided into slots (12 seconds each) and epochs (32 slots = ~6.4 minutes); (3) Block proposal — each slot, one validator is pseudo-randomly selected to propose a block (RANDAO randomness); (4) Attestation committees — each slot, a committee of ~512 validators attest to (vote on) the head of the chain; (5) Finality (FFG) — Casper FFG provides economic finality: after 2 epochs (~12.8 minutes), a block is finalized. Reversing finality would require slashing 1/3 of all staked ETH (~millions of ETH); (6) Fork choice (LMD-GHOST) — Latest Message Driven Greedy Heaviest Observed SubTree selects the canonical chain head; (7) Slashing — validators that double-vote or sign conflicting blocks have ETH slashed and are forcibly ejected. The Merge reduced Ethereum's energy consumption by ~99.95% while maintaining security through economic incentives instead of compute.