Blockchain is a technology that securely transfers data based on a very complex coding system, similar to a company's accounting ledger, where cash is closely monitored. In this case Blockchain is an accounting ledger operating in the digital domain.
Blockchain owns a very special feature that is the transmission of data does not require an intermediary to confirm the information. The Blockchain system has many independent nodes that can authenticate information without requiring a "sign of trust". The information in Blockchain can not be changed and only be added with the consent of all nodes in the system. This is a high security system against the possibility of data theft. Even if part of the Blockchain system collapses, the computers and other nodes will continue to protect the information and keep the network going.