Blockchain is a new form of database technology that enables multiple parties to share a single “golden copy” of data and trust that it is valid, owing to a breakthrough of computer science that enables the computers of multiple users or organizations to reach consensus about the state of their shared data without the need to reconcile their own copies.
Bitcoin was the first application of blockchain technology. It is a decentralized payments system that records the ownership and transfers of a token (called a bitcoin) on payments system fully integrated with the token (called a blockchain) that is operated by thousands of computer nodes located around the world.
Security is always relative. Computer science experts view blockchain systems as relatively more secure than traditional computer networks. Blockchain systems are decentralized and protected by encryption, while traditional systems are centralized and the information stored inside their firewalls is rarely protected by encryption.