People use the term "blockchain technology" to mean different things, and this can be confusing. Sometimes they talk about Bitcoin Blockchain, sometimes it's the Ethereum Blockchain, sometimes it's other virtual currencies or digital coins, sometimes it's smart contracts. Mostly, they talk about distributed ledgers, a list of transactions.

In fact, a blockchain is a register of facts (transaction), replicated on several computers connected to each other by a peer-to-peer network. Network computers are called nodes. The communication between the nodes is encrypted and guarantees the identity of the sender and the recipient. When a node wants to add a new fact to the register, it proposes it to the network which forms a consensus to determine where (and especially when) this fact should be entered in the register. This consensus is called a block, the blocks are ordered in a single string, which is replicated throughout the network. Each block points to the previous block.

The node that assembles the facts (transactions) into "blocks", by adding a header that contains the block size, the number of transactions it contains, the date and time, a checksum (" Hash ") which will serve as the unique identifier of the block, and the identifier of the previous block, is called the miner.

 To deepen the subject, look at this excellent introduction video on Bitcoin, where also explain what the blockchain.   

   

don't forget Upvote comment resteem....