Note that basic HTML can be created with a simple text editor. Plain text can be put on the web immediately. The .txt suffix identifies the file as plain text without formatting - and any web server will be able to make this text available without any further effort. HTML-formatted text needs slightly more work. A plain-text file can be made into a formatted HTML file by, at a minimum, entering a title and a heading and renaming the file to have a suffix of .html rather than .txt.
Titles appear as names of the document window.
Headers help organize the text. Anchors may appear within a paragraph, a list, etc. HREF refers to the actual file location. We use them extensively to organize links and data. Images placed online are first converted to GIF since it is widely used on the web.