A blockchain "block" is similar to a hard drive that we use to store data. Each block is the place where the information on the blockchain is stored. This information is encrypted by cryptography to ensure that the data stored cannot be tampered with.
The blockchain system examines all the data generated during the period, such as transaction records and records of when the block was edited or created, and stores this data on a new block. This block is linked to the previous block, and each block must contain information about the previous block to be valid, thus forming a chain, hence it's called the "blockchain".
Blockchain is essentially a decentralized database. The scenario where blockchain can really shine is when it allows users to collaborate without the involvement of a third party intermediary and without having to trust each other. In a blockchain network, no party can tamper with the data on the blockchain.
Users who want to run and independently verify the state of the blockchain must download a specific wallet software. Once the software is launched, it will access the other computing devices in the blockchain network for the purpose of uploading or downloading information (e.g., transactions, blocks). The software will download a block of data, check its authenticity, and then broadcast the verified relevant information to other computing devices.
Thus, we get the blockchain ecosystem consisting of hundreds, even thousands of computing devices. These computing devices are called "nodes" and run the same software and simultaneously update and broadcast transaction data to each other, realizing the true and decentralized nature of blockchain data.