Blockchain – Basics

If we look at the word blockchain, it gets simplified to a chain of blocks. A block in the blockchain is a node that contains, data, hash, and previous hash. This previous hash information helps these nodes connect to each other, hence forming the chain.

blockchain is a type of distributed ledger technology (DLT) that consists of growing list of records, called blocks, that are securely linked together using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data

https://en.wikipedia.org/wiki/Blockchain

Blockchain is a shared, immutable ledger that facilitates the process of recording transactions and tracking assets in a business network. 

https://www.ibm.com/in-en/topics/what-is-blockchain

Three terms we are hearing here

Ledger: In simple terms, a ledger is a book of records. In this case, a record is a block. And blocks chained to each other (blockchain) form the ledger.

Distributed: This is where things get interesting, this ledger is not dependent on one machine available in multiple machines, hence distributed in nature.

Immutable: Records or Blocks are immutable. This is because updating a record means corrupting the hash (hence the whole chain is corrupted).