What HTML is
Hypertext Markup Language. The lingua franca for publishing hypertext on the World Wide Web. HTML is a nonproprietary format based on SGML. It can be created and processed in a wide range of software programs, from simple plain text editors to WYSIWYG programs to sophisticated authoring tools.
HTML is a mark-up language (versus a programming language) that uses tags to structure text into headings, paragraphs, lists, and links (like those seen on the NetLingo.com HTML Code Cheat Sheet). It tells a Web browser how to display text and images. You can see a Web page's HTML code if you select "view source" from the View menu in your Web browser.
A question that often comes up is how to make HTML code be visible on a page and not execute? You do this by using the ASCII code equivalents of the "less than" and "greater than" symbols (this way it is interpreted as just text and not real HTML code).
The meaning of Code or coding
The act of creating computer programs, Web sites, and other applications. "Code" refers to the typed program instructions that programmers write. The written code is interpreted into a language that a system can read and execute. A favorite term among Web developers, code is often mentioned with interesting verbs. For example, you may hear programmers say, "We're busy slinging code," which means they are writing a computer program or programming a database or Web site.