What is blockchain?
The concatenation is done via cryptographic hash entries, a kind of checksum. Each hash entry is created from all records of a list entry and is kept in both the preceding and the following list entry. The list entries are thus unalterably welded together, similar to a chain.
Furthermore, blockchain is a completely redundant data storage. All data is held by all participants in the network and is constantly synchronized.
The real bottom line, however, is the programmability of the network via smart contracts. A smart contract is a small program that is imported into the blockchain and, like other data, is kept in the blockchain in a redundant and unchangeable form.
The interaction of smart contracts, data and events, i.e. predefined events, makes it possible to map certain processes in a forgery-proof and trustworthy manner, which until now could only be realized via intermediaries.
