What is Blockchain?

Blockchain is a distributed database system involving multiple nodes, originally conceptualized for Bitcoin and first proposed by Satoshi Nakamoto in 2008. A blockchain consists of a series of data blocks generated through cryptographic methods, with each block containing the hash value of the previous block. Starting from the genesis block, these blocks are sequentially linked to form a chain. Each block is created in chronological order, as the hash of the preceding block is unknown until its completion. These characteristics make double-spending in Bitcoin extremely challenging.

Blockchain can be categorized into three types: public chains, consortium chains, and private chains.

• Public Chain: A blockchain where anyone worldwide can read, send transactions for valid confirmation, and participate in the consensus process. Examples include Bitcoin and Ethereum.
  
  
• Consortium Chain: This type of blockchain involves pre-selected nodes, usually with cooperative relationships and reliable network connections. The data on these blockchains can be either public or restricted, making it a partially decentralized system often referred to as "multi-centered." Examples include Hyperledger, R3, and EEA.
  
  
• Private Chain: A blockchain where participation is restricted to a limited number of nodes, such as specific institutional users. Access and data usage are strictly managed through permissions.

In the early stages of blockchain development, foundational protocols were designed to facilitate simple payment functions. However, with the emergence of platforms like Ethereum, blockchain entered the "2.0 era." This evolution introduced robust underlying protocols and the concept of smart contracts, enabling developers to create diverse decentralized applications (DApps) without delving into the complexities of blockchain's underlying architecture.