How Does the Concept of ‘Finality’ Differ in a BFT System versus a Proof-of-Work System?

In a BFT system, finality is absolute and achieved instantly or very quickly once the consensus protocol is completed. Once a block is committed, it cannot be reverted.

Proof-of-Work (PoW) systems, like Bitcoin, have probabilistic finality. A transaction is considered final after a certain number of subsequent blocks have been mined (e.g. six confirmations).

This probabilistic nature means there is always a small, non-zero chance of a chain reorganization and transaction reversal.