# What is a blockchain?

Blockchain is a database divided into blocks. You can think of this database as a notebook, and each block is a page of this book.\
It stores the history of every coin transfer of every user since 2010. Absolutely every action…

![](https://miro.medium.com/max/1400/1*KLF0ZxxQM79fywHWsuBrew.png)

### Who keeps these databases? <a href="#id-972f" id="id-972f"></a>

Anyone can store a database. The entire history of blockchain is in the public domain. There are different reasons for doing this, but the main one is to ensure the viability of the blockchain and to make a profit. That’s what the “miners” do..

### How does the mining process work? <a href="#id-9c82" id="id-9c82"></a>

A miner is not a human being, but a special computing machine whose only function is to pick up letters and numbers very quickly. And a mining farm is a large number of these machines in one place. And so it is customary that the people who own these machines are called “miners”.

<div align="center"><img src="https://miro.medium.com/max/1380/1*qsw4mfO5mQ672-vTE3ie1A.gif" alt=""></div>

And so imagine that James wants to transfer 1 bitcoin to Adam, the coin does not go to Adam immediately, but first goes to the network, where a random miner picks it up and processes it.

### Who processes transactions? <a href="#id-3a2b" id="id-3a2b"></a>

The miner accesses the blockchain database, that is, its history, and checks to see if James actually has 1 bitcoin in his wallet. If the result is positive, the miner sends a confirmation back to the network. Then other miners start working, whose task is to check if the first one is cheating. If everything is correct here, then 1 bitcoin goes to Adam’s wallet, and James pays the miners’ commission.

> In addition to the commission James pays, the miner receives a reward from the blockchain itself if he was the last person to process a transaction in the current block

But if James doesn’t have 1 bitcoin in his wallet, and he tries to transfer it to Adam, the first miner will surely discover this deception, and cancel the transaction.

### Can James negotiate with the miners to lie that he has 1 bitcoin? <a href="#id-60f6" id="id-60f6"></a>

No, the convenience of blockchain is that there are hundreds of thousands of miners working all over the world, there are 1 million miners mining bitcoin. They don’t choose which transaction to process.\
This is the most obvious manifestation of a *decentralized* network.

### Is it possible for someone to delete blockchain history? <a href="#dde0" id="dde0"></a>

Due to decentralization, to remove something, you need to negotiate with at least 50% of the miners, and as you have already understood — it is impossible!
