Finality in blockchain refers to the point at which a transaction is considered irreversible and permanently part of the blockchain. Once a transaction has finality, it cannot be changed, canceled, or double-spent—it’s guaranteed to be part of the canonical chain
There are two main types of finality:

1. Probabilistic Finality:

Used in blockchains like Bitcoin and Ethereum (pre-Merge). 1.

A transaction becomes more "final" as more blocks are added on top of it. 2.

There's always a small chance of a chain reorganization, so finality is not 100% guaranteed, but becomes extremely unlikely over time (e.g., 6 confirmations in Bitcoin is generally considered final). 3.

2. Deterministic (or Absolute) Finality:

Used in proof-of-stake systems with Byzantine Fault Tolerance (BFT) algorithms (e.g., Ethereum 2.0, Tendermint, Polkadot). 1.

Once validators agree and finalize a block, it’s impossible to reverse without significant validator misbehavior (usually with slashing penalties). 2.

Finality is instant and guaranteed once reached. 3.

Irreversible Confirmation:
Finality signifies that a transaction has been successfully validated and confirmed by the blockchain network, making it impossible to reverse or change