What is a Blockchain?

A blockchain is a type of database — but with very specific properties that make it special.

Traditional Database vs Blockchain

Traditional Database (like a bank): Owned by one company, can be edited or manipulated, you must trust the company.

Blockchain: Shared across thousands of computers simultaneously, data is permanent — once written, cannot be changed, no single owner — governed by rules (code).

How it Works

Imagine a chain of boxes. Each box (block) contains a batch of transactions, a timestamp, and a fingerprint (hash) of the previous box. The chain is formed by each block referencing the one before it. If you try to change a transaction in block 100, you'd have to change the hash — which would break block 101, which would break block 102... all the way to the present.

To rewrite history, you'd need to control 51% of the entire Bitcoin mining network simultaneously. With Bitcoin's size today, this is economically infeasible.

This is why blockchain is immutable — tamper-proof.