Proof of work as a physical leap into the digital realm 

Historically we had two forms of money. 
The list(ledger)
The Token(gold etc)
The list( ledger ) is efficient and can scale to all 8 billion of us but it's centralized and can be expanded at will.

The token can not be expanded at will but can not scale to all 8 billion of us.

Now when Satoshi decided to make money that is difficult to expand at will (token)but can scale to all 8 billion of us (ledger)
He had to find a way to collapse a token into a digital medium that can be teleported through the internet. 
He had to find a way to collapse a physical token into a ledger and he used proof of work to accomplish this.
Bitcoin is a physical token that was de-materialised through proof of work into a digital ledger so that we can now be able to move money through the internet. 

The internet only recognize bites of data hence Bitcoin is a physical token that was de-materialised through proof of work into bites of data to enable us to transfer money through the internet. 

So when transferring Bitcoin, you are actually moving bites of data from you to another person using your private and public keys as security and the one that receives it uses their private and public keys to secure it and once it moved to another wallet, it can't be reversed because the blockchain will have recorded that this piece of information has moved to here and time stamp it.
That is why the term blockchain is not even in the Bitcoin White paper. 
It's called *Time Chain*
It's a time stamp server, that records the movement of data or information or money.
This is called a chronological record of the order of events.