Hello world 

A blockchain is an array or a list with blocks in it. 

1. A block has information/content in it. 
2. A block has the ID from the previous block in It. 
3. A block has an ID and this is a hash of all information of a block. 

So, every block contains
the ID from the block before it which is generated with all its information which contains 
the ID from the block before it which is generated with all its information which contains
the ID from the block before it which is generated with all its information which contains
...

The first block has no previous block and is called genesis block. 


There you go. I hope i could explain the very basics of how a blockchain works. 
This post will be stored forever in the blockchain and without it the following blocks wont be valid :)