What is Blockchain for dummies

 A block chain is a book that is continuously growing list of records called blocks which are linked and secured using crypto cryptography. So this is a very general definition.So let's have a look at one of these records are so-called blocks what constitutes a block Well a block because it's a record.
We'll obviously have a data inside it.
For instance it might have just a string of words hello world.

                                

Then it will have a value which is called a previous hash and we'll get to this in a second and then we'll have a value which is its own hash. And what the hash is is it's like a fingerprint of this block.
It's like taking the first two elements the data and the previous hash and finding the like a number which represents that data.
So a shortened version of that data specifically 64 characters long.

But basically right now the best way to think about it is a hash a digital hash is like a fingerprint of some amount of data.And that makes its much clearer or makes it clearer now what's going on.

So the block here has its own hash and then the previous hash which is contained within the block as a reference is actually the hash of the block that came before it. So let's have a look at that in action.So here we've got block number one.
                                                                                   
It's also called the Genesis block in a box in the first block and it's called jazzes block because after the block chain is initialized that block will always stay blocking them on forever and ever and 
ever for eternity it will never change.That's no other block will become the once. This block is always going to be the first one.
That's where it all originate. 
                                    

You might have some data in it. We're not going to go into detail what kind of data is in there but assuming there's some data it doesn't  have a previous hash inside this block because this is the jettisons block is the only block that will have a previous hash.

So we're just going to present them all zeros and then it will have its own hash again. For now let's think of hash as a fingerprint.
This time it does have a previous hash and it has its own hash again.And as you can see the block is the previous hash of block number two is exactly identical or is exactly

Blocks Cryptographically linked together

block number ones hash and that is where the link comes. That is why abortion is called a chain or a block chain because the blocks are cryptographically linked with each other through these hashes.
And again more of that not to come.
But this is conceptually hard works every brought block has its own fingerprint and it also references the fingerprints of the previous block. So if anything were to change and block number one it's fingerprint would change.  So somebody were to tamper with the data.This fingerprint would change and it would no longer match this fingerprint. 
So this block would know or we would know by looking at this block that somebody tampered with this block. And then again looking at the three data it's got the previous hash it's got its own hash and it's linked to the so on and so on.
So again Conceptually we can see that if anybody were to tamper with any block this one and this one then the fingerprints would no longer match up and the chain would be invalid the chain would show that there's something wrong.
That's why we say that blocks are cryptographically linked together.
There are many more concepts to blockades and things like mining distributed peer to peer network consensus protocol immutable ledger and hash cryptography.