Explanation
Without a central party, consensus is the core of the system. Changing those rules requires a broad majority; when that fails, a fork appears.
01
The problem being solved
Thousands of computers that do not trust each other must agree on one ordering of transactions, while messages may arrive late or falsified. Consensus rules determine which block is valid, what happens with two competing versions and when a transaction counts as final.
02
Finality
In Bitcoin finality is probabilistic: each additional confirmation makes reversal exponentially less likely, which is why exchanges often wait six blocks. Modern proof-of-stake networks have an explicit moment at which a block is declared irreversible. For payments and institutions that difference is decisive.
Key takeaways
- Rules decide validity, not a single party.
- More confirmations = more certainty.
- Finality differs sharply per network.