A blockchain is a cryptographic ledger system, using cryptic code and a network of computers to securely store and verify information. On blockchains users are able to publish applications, similar to those that run on your phone or computer- on the blockchain they are called ‘Smart Contracts’. These contracts allow users to move beyond simply buying and sending units of currency like Bitcoin. The blockchain allows users to run or build full-scale applications, offering financial services such as loans, voting protocols, supply chain management, and a wide variety of other use cases.
For more information, check out an extensive series on Crypto Basics by Coinbase.