What's a block?
A block is where the information is stored.
Imagine a clear transparent box that contains a bar of chocolate, once you have taken this bar of chocolate out, you fill the box with other items, you lock the box, throwing away the key.
The block is locked, and the transaction that took place can never be altered.
You can always view what’s now in the block, as it's transparent, but can never change the contents after you have sealed it.
In cryptocurrency, the block contains a reward of nibbles, instead of a bar of chocolate.
This reward is taken by the miners and replaced with transaction data.
An amount of NibbleClassic has been sent from somewhere, to somewhere else.
What makes up a blockchain?
Once a block has been found through the mining process, and the transaction data has been locked away, work begins on finding a new block.
The process repeats, forming a string of blocks, all with the reward being taken, and replaced with transaction data.
String of blocks - chain of blocks - blockchain
Where does the transaction data get stored?
It's only the data of the transaction that gets stored, and this gets stored in a block.
As the block is transparent as such, anyone can view the transaction data.
The data will show that a transfer took place. It doesn't show the person it came from, or how much, or who to and how much, and neither does it show the balance anyone holds.
The block only holds the history and shows that the transaction took place, and cannot be undone.
This data is viewable through a block explorer, and is publicly available.