"Blockchain" translates to "blockchain." The technology itself was invented back in the 90s. But widespread use and the very concept of "Blockchain" was first used by Satoshi Nakamoto after Bitcoin (Bitcoin) appeared in 2008 - the first and most famous cryptocurrency, a new form of digital money, which is not controlled by anyone and has a limited issue. But we'll talk about bitcoin later.... Blockchain is a decentralized database. Decentralization is when there is no third party, i.e. there is no manager, administrator or any other controlling body. Moreover, decentralization implies that there is no server that can be shut down at will. There is no such thing. All information is stored on the computers of all network users located in different parts of the world. The main principles of the technology are:

• decentralization

• distribution

• security

• transparency

• immutability Each block in the blockchain consists of 2 parts - HEAD and PAYLOAD (header and body) HEAD:

• version number

• block generation date and time

• block hash

• hash of the previous block

• hash of all blocks ever created

• nonce and bits

  PAYLOAD

  all transactions that fell into this block (e.g. Vasya sent 1 bitcoin to Masha, Kolya sent 0.5 bitcoin to Alena, etc.). In other words, a continuous chain of blocks is a kind of ledger that records all transactions that have ever been made in the system. A huge advantage of the blockchain is that it is virtually impossible to hack. Why is it virtually-- there is such a thing as attack 51. But we'll talk about that separately. By the way bitcoin has never been hacked and is unlikely to be hacked, even anticipating your question about quantum computers. If suddenly you want to octate a block with a certain transaction, given that each subsequent block contains a hash function of the previous one, you will need to change all subsequent blocks, which you can hardly do)))) But if you still send you a very large amount and you are very worried that maybe something will go wrong. Then wait for the signing of a few more blocks after yours in the blockchain and then you can confirm receipt and continue to do your business. So.... I think we're missing something. Hash is a set of numbers and letters that is formed by passing through a hash function, in simple words a program that converts any data..... for example "hello everyone, my name is maxim" into a set of numbers and letters (for example this is hash function sha 256( such is used in bitcoin) will look like this 14F745AD47876478C14EA32F4C2A97A9BDA4525224C7EB69D7BAA580F82D616D. and if we put an exclamation mark at the end of this sentence "Hello everyone, my name is Maxim!" we will get a completely different hash CFD320020DDC4213F105CDAF432E673D2708EF0842DF9BD4BEFD81B8D370B52D. If we are talking about a block in the bitcoin blockchain, the hash contains all the information about the block, date, transactions included in the block, hash of the previous block, etc. Try experimenting! https://passwordsgenerator.net/sha256-hash-generator/ Any change, even the smallest one, will completely change the set of these letters and numbers. And it is precisely these very blocks in the blockchain that are signed by POW miners or POS vlidators.

• POW Proof of Work

• POS Proof of Stake

  POW and POS are consensus mechanisms. Consensus in blockchain is an agreement by a majority of the network participants regarding the distribution of data that leads to the validation of a transaction. A consensus algorithm is a kind of mechanism that lays down the rules of the network and the conditions under which a common agreement can be reached. These are the 2 most common algorithms, but there are others that we will not focus on. Delegated Proof-of-Stake (DPoS), Proof-of-Authority (PoAuthority), and more

• The first block in the blockchain is called the genesis block. To summarize, blockchain is decentralization, security, transparency, reliability and immutability.