EPP code or Extensible Provisioning Protocol code is authorization code needed when transferring your Domain to a new host.
Website hosting is simply where your website is housed. Just like a home is housed on a piece of land, a website is hosted (or housed) on computer servers of website hosting companies.
Data Centre is a complex of computer servers that host the internet. Think of your computer, it's small because there is a small amount of information stored. But what about websites like Facebook? Amazon? Google? These have a massive amount of data. The computers for these websites are many, and they are stored in what is known as Data Centers.