Master Blockchain Fundamentals
An interactive guide to understanding the core concepts behind the technology that’s changing the world. Start your journey from the ground up.
Start LearningWhat is a Blockchain?
At its core, a blockchain is a distributed, unchangeable digital ledger. Think of it as a shared book of records, but one that’s duplicated and spread across many computers. This section introduces its three fundamental properties. Click on each card to learn more.
🔗 Decentralization
Instead of one person or company in charge, the ledger is shared and maintained by a network of computers (nodes).
This means no single entity has control. Data is copied across the network, making the system highly resistant to censorship or failure. If one node goes down, the network continues to run.
🔒 Immutability
Once data (like a transaction) is recorded in a block and added to the chain, it is practically impossible to change or remove.
Each block is linked to the one before it using a unique code called a ‘hash’. Changing a block would change its hash, which would break the link to all following blocks. This makes the data tamper-proof.
TRANSPARENCY
For public blockchains, anyone can view the ledger and all its transactions at any time.
While users’ real-world identities are hidden (pseudonymous), the history of all transactions is open for public audit. This builds trust, as everyone is playing by the same rules and can verify the records for themselves.
How It Works: Building the Chain
A blockchain is built, as the name suggests, from a chain of blocks. This section provides a simplified, interactive look at how blocks are added and how the network agrees on which blocks are valid.
1. The Chain of Blocks
Each block contains data, its own unique hash (a digital fingerprint), and the hash of the block before it. This “previous hash” is what links the blocks together, forming a secure chain. Click the button to add a new block.
Data: …
Hash: 0xabc…
Prev: 0000
2. Network Consensus
How does the whole network agree on which new blocks to add? This is achieved through a “consensus mechanism.” The two most common are Proof-of-Work and Proof-of-Stake. Use the toggle to compare them.
Proof-of-Work (PoW)
Used by Bitcoin. “Miners” compete to solve a very complex mathematical puzzle. The first one to find the solution gets to add the next block to the chain and is rewarded. This process requires significant computational power and energy, but is extremely secure.
Core Components
Beyond blocks and chains, a few other key pieces make the system work. This section breaks down the main components you’ll hear about.
The Block
The fundamental unit. It’s a container for data. A block typically contains:
- Data: A list of transactions.
- Hash: Its own unique ID.
- Previous Hash: The ID of the block before it.
- Timestamp: When it was created.
Digital Signatures
This is how the network proves you own your assets and authorized a transaction. It uses:
- Private Key: A secret password you must *never* share. Used to “sign” (approve) transactions.
- Public Key: Your “address” (like a bank account number) that you can share to receive funds. It’s generated from your private key.
Nodes & The Network
A “node” is simply a computer participating in the network.
- Full Nodes: Store a complete copy of the *entire* blockchain ledger. They validate all new transactions and blocks.
- Miners/Validators: Special nodes that work to create new blocks (via PoW or PoS).
This distributed network of nodes is what makes the system decentralized.
Types of Blockchains
Not all blockchains are created equal. They are often designed for different purposes, which affects who can participate and see the data. The chart below compares the most common types based on key attributes.
Real-World Use Cases
Blockchain is more than just cryptocurrency. Its properties of decentralization and immutability are useful in many industries. Here are some of the most prominent applications. Click any card to see more detail.
Cryptocurrency
The original use case. Bitcoin and Ethereum are decentralized digital currencies built on a blockchain.
They allow for peer-to-peer transactions without a bank or central authority. The blockchain acts as the public ledger, recording every transaction securely and transparently.
Smart Contracts (DeFi)
Self-executing contracts with the terms of the agreement written directly into code. (e.g., Ethereum).
They automatically run when conditions are met. This powers Decentralized Finance (DeFi), enabling lending, borrowing, and trading without traditional financial intermediaries.
Supply Chain Management
Tracking goods from origin to destination on an immutable ledger.
This increases transparency, allowing companies and consumers to verify the authenticity and journey of a product (e.g., “farm-to-table” food, luxury goods). It helps prevent fraud and improves efficiency.
Try It: The “Hash” in Action
A “hash” is a core part of what makes a blockchain secure and immutable. It’s an algorithm that turns *any* input data into a unique, fixed-length string of text. Try it yourself. Notice how even a tiny change (like adding a period) completely changes the entire hash.