What are the parts of a Blockchain? In the following article What Are Bitcoins? How Do Bitcoins Work?, it is mentioned that a blockchain is composed of three parts:


Identifying address
History
Private key header


Although, after taking a look at this question "Can someone explain how the Bitcoin Blockchain works?"
  it doesn't reflect what that article mentions. 

If those three parts are the actual parts of a blockchain, can someone provide a better explanation for each one?
They are not. They might be provided to try to provide a better explanation, but I don't even think that this purpose is achieved. There are several sentences throughout the article that make no sense at all, like:


  A bitcoin, at its core, is a very simple data ledger file called a 'blockchain'. A blockchain's file size is quite small, similar to the size of a long text message on your smartphone.


I would recommend you to look at the question you mentioned , that actually have two really good answers, and ignore the first article.