Simple: It’s the language that’s used on the web. All web pages use this language and have since the Internet was born back in the mid-nineties. It’s been updated a few times.
That said, there are a few programming languages that are used in addition to HTML. The letters stand for HyperText Markup Language. There’s really nothing complicated about HTML, but I’m not inclined to use it as my second language.
Note: It LOOKS simple, but word processing documents, Power Point presentations and PDF’s don’t translate into HTML. So, don’t try to paste your Power Point onto the Internet. The Internet will look at you as though you’re speaking a foreign language. Because you are.
Interesting note: Google and the other search engines read HTML (and a handful of other languages used on the web). Google can NOT read pictures or text that’s part of a picture.
EVEN more interesting note (there’s $ involved): Since my job is to make you successful, I strongly discourage you from ignoring good HTML practices by posting a lot of pdf’s or images on your website. Create (or hire someone to create) good, solid HTML and your site will rank better in searches, be found by the people who want to buy your product and everyone will win.