What Is Blockchain Technology and How Does It Work?

A blockchain is a type of database. But instead of being stored on a single computer or controlled by one company, it is copied across thousands of computers simultaneously and updated by agreement. That is what makes it special.

What problem does blockchain solve?

Imagine you want to send money to a friend in another country. Normally, you would go through your bank. The bank checks your balance, deducts the amount, and credits your friend’s bank. You trust this process because you trust both banks.

But what if there were no banks? You would need some other way to make sure you cannot spend the same money twice, and that both parties agree a transaction happened. This is the problem blockchain solves.

How a blockchain works, step by step

1. You broadcast a transaction: You tell the network you want to send 0.01 Bitcoin to your friend’s address.

2. Nodes verify it: Thousands of computers on the network independently check that your address actually holds 0.01 Bitcoin and that you have not already spent it elsewhere.

3. Transactions are grouped into blocks: Verified transactions are bundled together into a block approximately every 10 minutes (for Bitcoin).

4. Miners compete to add the block: Computers called miners compete to solve a complex mathematical puzzle. The winner gets to add the new block to the chain and receives a Bitcoin reward.

5. The block is permanently recorded: Once added, the block becomes part of the chain. Every computer on the network updates its copy. Altering it would require redoing the work for that block and every block after it simultaneously, which is computationally impractical.

What is immutability?

Once data is written to a blockchain, it is extremely difficult to change. This property, called immutability, is what makes blockchains trustworthy for recording transactions: no single party can quietly alter the history.

What are smart contracts?

On some blockchains, like Ethereum, you can also write self-executing programmes called smart contracts. These are bits of code stored on the blockchain that run automatically when certain conditions are met. For example, a smart contract could automatically release payment to a freelancer once a delivery is confirmed, without anyone having to trust either party.

Is blockchain the same as Bitcoin?

No. Bitcoin is a cryptocurrency that runs on one particular blockchain. But the same technology underpins thousands of other projects, from Ethereum to Solana to Cardano. Each has its own blockchain with different rules, speeds, and purposes.

If you want to go deeper, the next step in our learning path is our guide to Bitcoin, explained for absolute beginners.