A blockchain is a database of information stored across a network of computers (nodes), across the world. It holds a set of data or information along with blocks that keep a record of the transactions that have been made in the database. A blockchain is like a chain made up of interconnected pieces of information.
The use of a group of distributed computers to store data is one of the major differences between blockchain and traditional databases. A blockchain has many copies across hundreds or thousands of computers and a change can only be made when a majority of computers accept the change.
You may also hear blockchains called ledgers, or distributed ledger technology (DLT).
The basic process of storing data on a blockchain looks like this:
A list of actions is completed and recorded in a chunk (block)
The block is completed when the data capacity is reached, e.g. 100 transactions
The block is then inserted into the blockchain in chronological order, forming a continuous chain
This sequential arrangement ensures that the blockchain is always connected in a time-based sequence, making it extremely difficult to alter or manipulate the data. The blocks are interconnected in a chain, with each block linked to the next using a special code called a hash.