What is a Blockchain?

A blockchain is literally a chain of blocks.

Think of it as blocks lined together piece by piece and each block is unique and a continuation of the previous.

Now you might be wondering, what is inside these blocks? You can literally think of these blocks as storage units that stores data so we can store different kinds of things in these blocks.

You may have heard of data storage in Computers, a data storage is just data held in a computer. A blockchain is an open and decentralized data storage. Data in a blockchain are stored in chains of blocks spread across many computers network, instead of on a single computer. Because this data storage is open and decentralized, anyone can access, read, and store information in it at any time.

Each blockchain has a consensus mechanism, a way in which this distributed network agrees on what new information is written on that data storage, ensuring that the data is true and therefore trustworthy.

It is stated in the bitcoin whitepaper, a double spend should never happen. This is due to the bitcoin decentralized ledger, every node connected to the network ensures that no coins have been double spent.

Unlike a normal data storage, data stored in a blockchain are immutable, so once a data get into one of these blocks, it can't be changed. Everyone(or majority) participating in the network gets a copy of these data, so if an individual try to change theirs, there will be a conflict with the rest(majority) and they may get kicked out of the network.

In blockchain, a single point of failure is also not possible. In the bitcoin blockchain for example, there are thousands of nodes(severs) connected to the network. If a particular node goes down, the network does not go down, other nodes will continue to run.