Integrity and trust
How do we know if the systems we rely on have any integrity and honesty? How do we trust that votes are counted correctly and honestly? How do we identify someone? How do we know that who they say they are is true? Online or in the real world? How do we trust claims by corporations, certificates, and labels like "fair trade"? What makes us so sure of the origin of the coffee we have? If you really want to answer those questions and be really sure about your answers, you need a system better than what we have now. A system where records can be stored, facts can be verified, and security is guaranteed. Where no one will be able to beat the system and everyone will be an avid police of the system.
A system that stores information across a network of personal computers making them decentralized and distributed. That means no single owner and no central point of failure. Everyone contributes to run it.
Records are stored in a bundle of chronological chains called blocks. The blocks are secured by encryption which ensures that blocks are not tampered with.
The first and most popular application of blockchain is bitcoin. It is a form of digital money that is not owned by any bank or financial middleman. You can easily send it to anyone around the world. It is not just a way to send money though. Bitcoin uses blockchain to validate transactions and tracking ownership. TO prevent owning money twice like counterfeit money in physical money form.
Other applications of the blockchain
Bitcoin is just the beginning. Blockchain can be used to make self-driving cares safer, to build a system of online identities, and track the millions of devices on the internet of things.