One-Sentence Definition
A blockchain is a chain of blocks containing transaction data, linked together using cryptographic hashes to create a permanent, unchangeable record that everyone can verify.
Why It Matters for Solo Mining
As a solo miner, you’re literally trying to add the next block to the blockchain — that’s your whole job. When you successfully mine a block, you’re extending the chain and earning the block reward plus transaction fees. The blockchain is also what proves you actually won, because once your block gets added and receives confirmations, nobody can take that away from you.
How It Works
Each block in the blockchain contains a block header with important data like the Merkle root, timestamp, and a reference to the previous block’s hash. This creates an unbreakable chain — if someone tried to change an old block, it would change that block’s hash, which would break the link to the next block, and everyone would immediately know something was wrong.
The chain starts with the Genesis Block and grows one block at a time. Every full node on the network has a complete copy of the blockchain, which they use to verify that new blocks follow all the rules. The block height tells you how many blocks exist in the chain.
Miners compete to find the next valid block by trying different nonce values until they find a hash below the target. When multiple miners find blocks at the same time, you might get a temporary fork, but the network eventually agrees on one main chain. Blocks on the losing fork become orphan blocks.
Example
Think of a blockchain like a public notebook where every page (block) is glued to the previous page with special glue (cryptographic hash). You can add a new page, but you can’t rip out or change old pages without everyone noticing. Bitcoin’s blockchain started in 2009 and now contains over 800,000 blocks — that’s a really long notebook!