HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. HTML is the basic building-blocks of webpages.
HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content. HTML tags normally come in pairs like <h1> and </h1>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags). In between these tags web designers can add text, tables, images, etc.
The purpose of a web browser is to read HTML documents and compose them into visual or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.
I mention HTML because people still post jobs for web developers and specify that they must know HTML. I do know HTML and I have been working with it for as long as I have been working in Web Development. I know how to read and write code and if pressed, I could create a decent looking web page using just a text editor. For the most part I use software to turn what I am making into HTML.
I also know how to manipulate HTML in other ways. I am familiar with making a web server send HTML emails and newsletters. I know how to create PHP code that will alter HTML based on certain conditions. I know how to make HTML editors which will add HTML tags for writers.