We have elected to put our money and faith in a mathematical framework that is free of politics and human error. - Tyler Winkelvoss, Rower & Entrepreneur
Blockchain is an open, decentralized and immutable database. A database is just data held in a computer.
The blockchain database is open, meaning anyone can access, read, and store information in it at any time. The database is decentralized, meaning that it stores information across a distributed computer network, instead of a single device. This database is also immutable, meaning that data written on the network can't be changed.
In a blockchain, data are stored in blocks. It is literally a chain of blocks. Think of it as blocks of data lined together piece by piece and each block is unique and a continuation of the previous.
The more decentralized a blockchain is, the more difficult it is to experience a single point of failure.
Also, in a blockchain, a double spend should never happen. This is due to the decentralized ledger, the network through its consensus mechanism ensures that no coins have been double spent.
Each blockchain has a consensus mechanism, a way in which the network agrees on what new information is stored on that database.
At this point, this may not be easy for you to grasp. But just know that a blockchain allows anyone to do trustless transactions that are open, decentralized, and unchangeable. Trustless, means that we trust code and computer networks rather than trusting a middleman or single entity like a bank or Paypal.
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