> ## Documentation Index > Fetch the complete documentation index at: https://docs.carletonblockchain.ca/llms.txt > Use this file to discover all available pages before exploring further. # How the Blockchain works > A high level overview of the technical aspects of Blockchain. # What is a Blockchain? Resources Used: > TLDR : Imagine a blockchain is like an append only, singly linked-list that anyone in the world can see. # Key Concepts ## Hash A hash is a fingerprint of some digital data. Regardless if the input data is 1 char or an entire library, a unique hash will be generated. SHA-256 (Secure Hash Algorithm 256-bit) produces a fixed-size 256-bit hash value. ```math theme={null} 2^{256} = 1.1579209 \times 10^{77} \space \text{combinations} ``` According to [Bitbo](https://bitbo.io/how-many-users), there is reportedly 200 million active Bitcoin addresses. The chances you randomly guess/brute force a seed phrase is about: ```math theme={null} 1/8.6 \times 10^{-78} ``` > TLDR: The odds someone hacks your Bitcoin address through guessing/brute force is essentially 0.

## Block A block is a container that holds a list of transactions or data records. ### Components * **Data**: Transactions or records that the block stores * **Nonce**: A value used in mining to find a valid hash * **Hash**: Digital signature combining block number, data, previous block's hash, nonce, and timestamp

## Blockchain A chain of blocks that are cryptographically linked together. Blockchains are "immutable" because changing ANY data in a block will: * Change the hash of that block * Invalidate all subsequent blocks * Each block can hold \~4,000 transactions (1MB limit)

## Distributed System The network is distributed, meaning: * Anyone can see the blockchain * The network accepts the majority consensus * The longest chain is typically considered valid