What HTML does
On a recipe page, HTML can mark “Ingredients” as a heading, the ingredients as a list, and “Print” as a button. These markers are called tags. The browser reads them to build the page you see.
HTML is one markup language. The similarly named Markdown uses plain text symbols to mark headings, links, and other formatting.
Why the labels matter
The labels help screen readers and search engines understand the page. They also let browsers recognise controls such as buttons. A content management system can supply the words and images. CSS controls much of the page’s appearance, including colours and layout.