What is Blockchain? Can we learn blockchain through this app? Pls tell

Answer 1

You will probably want to first find out what blockchain is before deciding if you want to learn more about it. There are multiple resources that give a summary about _what_ blockchain is.
https://en.m.wikipedia.org/wiki/Blockchain
https://www.ibm.com/topics/what-is-blockchain
https://www.bitdegree.org/crypto/tutorials/blockchain-explained

I am not aware of any blockchain course on sololearn but other users may have provided learning resources on it.

Answer 2

There doesn't appear to be a course on the app, so no. You will have to look for external sources. Be aware that blockchain is a heavily obfuscated term, and often people are not really talking about the structure when they say blockchain.

I find other explanations to not do justice as they often explain blockchain in terms of how it works for cryptocurrencies, which isn't really what it is. Decentralized ledger is NOT a useful explanation, as it relies on assumption that it is decentralized and related to finance.

Below I explains blockchain, in simple terms, in 3 comments:

Part 1:

Imagine you have 12 dice. Each column here represents a group (block).

(1) (2) (5)

(0) (1) (2)

(1) (6) (1)

(1) (2) (3)

There are 3 important parts of a blockchain. The "hash of the block" which is the hash of all other contents of the block. In this case, it is the top dice of each column. Essentially it is somehow determined by all the other values in a column. This value is always calculated.

Answer 3

Part 2:

Think of the hash as taking some content, and then transforming into something else in such a way where the following properties hold: Given the transformed version of the content, you cannot find out what the content was. Given the content, you can't find different content that gives the same transformed result. And finally, you can't find any two contents that have the same transformed result.

Next is the "previous hash". This is the 2nd dice in the column. The previous hash is equal to the top dice in the column before it.

The next important thing is the "block height", although this may have many names. This is represented in the last row. This is simply a unique value that every block has, typically counting up by 1; 1 + previous block. The purpose here is so that if you take all content of blocks, no two blocks have exactly the same contents (recall, the hash of the block).

The 3rd dice in a column is just any kind of information. Lets say the amount of money I sent to you as an example.

Answer 4

Part 3:

You could have any number of dice that represent any kind of information (like the 3rd dice).

We created a chain. How? Well if I change any dice, the system fails. If I turned the 6 into a 3, the hash of the block changes because it was calculated using the numbers [1,6,2], but now uses the numbers [1,3,2]. Lets say it changed to a 4. This means that the next blocks previous hash (2) is not equal to its hash (4).

So, the blockchain is invalid. In other words, it is protected from modifications. You can't change things, you just add more things.

That is what a blockchain *actually* is. Ie: The structure linked via hashing, creating a append-only chain.

This structure grew popular among cryptocurrencies, as Bitcoin proposed a method of using it in a permissionless setting with a decentralized network. having it used in this way creates more concerns worth exploring; such as, how do you determine whos blockchain is the real one (e.g longest)? And who/how add to the chain (e.g miners / proof of x)?