H is for HTML

HTML is the basic programming language of the web. It is the language of your web browser. HTML stands for hypertext markup language. The content that you want to put in your webpage is enclosed in HTML markup tags, and it is these tags (such as <p></p>, the paragraph tags) which tell the browser how to display or to present the content.

I say its the basic programming language because there are many other languages that can be embedded in HTML to do lots of whizzy things. HTML is perhaps the mother of a family of languages that work a website.

XHTML is a stricter version of HTML and at the same time it is a subset of another language XML.

In turn, XML stands for eXtensible markup language. Whereas HTML marks up content so that it can be displayed by your browser, XML describes content so that it can be used as data for a great many other applications. XML is not itself a database.