# What is a Blockchain?

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Blockchain is a type of shared database that differs from a typical database in the way it stores information, blockchains store data in connected blocks. As new data arrives, it is added to a new block. Once the block has been filled with data, it is chained onto the previous block, putting the data in chronological sequence.&#x20;

A blockchain may store several types of data, but its most popular application so far has been as a transaction ledger. Decentralized blockchains are immutable, which implies that data input is irreversible, and transactions are forever recorded and viewed by everyone.

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