Blockchain Glossary

On-chain data refers to all transaction information that is permanently recorded and validated on a blockchain network. This includes:

• Transaction amounts and timestamps
• Sender and receiver wallet addresses
• Smart contract executions
• Block confirmations and hash values

This data is publicly accessible and immutable once confirmed on the blockchain.

Block height represents the number of blocks in the chain preceding a particular block. It serves as:

1. A sequential identifier for blocks
2. A measure of blockchain growth over time
3. A reference point for network synchronization

The genesis block has a height of zero, with each subsequent block increasing the height by one.

Smart contracts are self-executing agreements with terms directly written into code that run on blockchain networks. Key characteristics include:

• Automated execution when predetermined conditions are met
• Transparent and verifiable code stored on-chain
• Immutable once deployed to the blockchain
• Execution results recorded as on-chain transactions

The primary distinction lies in where the transaction data is recorded:

1. On-chain transactions: Recorded directly on the blockchain, requiring network consensus and paying gas fees
2. Off-chain transactions: Processed through secondary layers or payment channels, settling outside the main blockchain

Off-chain solutions typically offer faster processing and lower costs but may sacrifice some decentralization benefits.

Mining is the process of validating transactions and creating new blocks on proof-of-work blockchains. Miners:

• Use computational power to solve complex mathematical problems
• Compete to add the next block to the blockchain
• Receive block rewards and transaction fees as incentives
• Secure the network through consensus mechanisms

Bitcoin mining currently rewards 6.25 BTC per block plus transaction fees.

A blockchain wallet address is a unique identifier that allows users to send and receive cryptocurrencies. Important features include:

1. Typically represented as an alphanumeric string
2. Derived from public keys through cryptographic hashing
3. Can be shared publicly to receive funds
4. Does not reveal the owner's private key or identity

Each blockchain network has its own address format standards.

Gas fees represent the cost required to perform operations on blockchain networks like Ethereum. They include:

• Computational resources needed for transaction processing
• Network priority pricing during congestion periods
• Incentives for validators or miners
• Protection against spam and infinite loops

A hard fork is a radical protocol change that makes previously invalid blocks/transactions valid, requiring all nodes to upgrade. Key aspects:

1. Creates a permanent divergence from the previous blockchain
2. Can result in two separate networks (e.g., Bitcoin and Bitcoin Cash)
3. Requires majority consensus from network participants
4. Often implements significant feature upgrades or fixes

Hard forks represent major evolutionary steps in blockchain development.