Look at the diagram
This is the literal diagram of the blockchain and this diagram itself is enough to explain what blockchain is. Here you can see that there are blocks and all of these blocks are connected to each other. This connection creates a network. So, blockchain is a network of blocks.
Now, What do these blocks contain and where are these blocks stored? These blocks contain data and these blocks are stored in computers.
To sum up, we can say that the chain of blocks (containing records of data) stored on networks of computers together is called a blockchain.
Now let's come to its fetaures to understand it more clearly...
Features of Blockchain:
There are 3 features of blockchain which makes it unique and useful. These 3 are the main features for which blockchain will stand out.
From the previous, diagram we could see that the data is divided among the network of computers. So, no particular authority has any hold of it. So, no one can control the data. Everyone has equal access to the data.
The data record which is stored in the network cannot be altered or forged. This happens due to complex cryptographic, hashing concepts.
In blockchain network, there is no central authority, and the data stored in blockchain cannot be forged or altered. If you have the correct credentials about the block then you will be even able to see the data of a block. Otherwise no one can see it.
Let's understand this by an example: Do you know where the government spends its money? Even if you ask the question to the government it can just tell you. But can you see it. Can you see how much transaction is made? No. If you ask the government to show the proof, it can literally change the data and show it to you since the goverment is the central authority and it has the power to change any of the bank records. So you can understand, this system is not much transparent.
But if it the bank records would be stored in blockchain, then government had to show us the actual record and it cannot modify the record of any transactions as blockchain eliminates the requirement of a central authority.
Let's conclude by a summery
Blockchain data, once verified is put up in the blockchain network, cannot be modified and since its distributed over a large network of computers, it is hard to destory thus making the blockchain network a transparent network and a more trustable network.