Crypto Foundations

A blockchain is a public ledger of transactions maintained by a network of computers instead of a single company. Each block bundles a set of transactions and is cryptographically linked to the block before it, forming a chain. Once a block is added, changing it would require re-doing the work for every block after it — which is why blockchains are described as tamper-resistant.

Key ideas:

• Distributed: thousands of nodes hold a copy of the ledger.
• Immutable: old blocks can't easily be rewritten.
• Consensus: the network agrees on which block comes next.

Bitcoin and Ethereum are the best-known examples, but the same pattern powers thousands of networks. Almost every crypto concept — wallets, gas, DeFi — builds on this foundation.