Blockchain is a mechanism that allows the storage of data electronically, in a manner that makes it hard for people or in the right words, impossible for people, to make changes within the system, or hack it.
It is a simple network of computer systems that allows the duplication and distribution of digital records of a transaction throughout the entire, exclusive, network. Each single block on the chain includes several transactions, where after every new transaction on the blockchain, the participants of the ledger also receive its copy.