What are HTML tags?

When a web browser displays a page (like this one right now), it reads from an ASCII, or plain text file. By the way, ASCII is pronounced: ASS-kee.

HTML stands for Hyper Text Markup Language. They key term is "Markup Language," because HTML is most definitely NOT a programming language. HTML mixes the content (like the words you are reading right now) with markup instructions to structure the presentation of that content (like the size, color, and paragraph formatting of the words you are reading right now).

and looks for "tags" that are marked by the < > signs. The basic format for a HTML tag is:

<tag_name>string of text</tag_name>

As an example, the centered title at the top of this page uses a header tag:

<h1>What are HTML tags?</h1>

This tag tells a web browser to display the text What are HTML tags? in the style of Header Level 1. HTML tags may tell a web browser to bold the text, italicize it, or make it be a hypertext link to another web page (among other things).

It is important to note that the closing tag,

</tag_name>

contains the / (read: slash) character. This slash tells a web browser to stop tagging the text. Many HTML tags are paired this way. If you forget the slash, a web browser will continue the tag for the rest of the text in your document, producing undesirable results.

NOTE: HTML tags are not case sensitive. That is - A web browser does not care if you use upper or lower case. For example, <h1></H1> is no different from <H1></h1>

Unlike computer programming, if you make a typographical error in HTML you will not crash the system; your web page will simply look... wrong.

Web browsers have a small but open vocabulary! An interesting aspect of HTML is that if the browser does not know what to do with a given tag, it will ignore it! For example, in this document you are viewing, the header tag for this section actually looks like this:

<wiggle><h1>What are HTML tags?</h1></wiggle>

Since your browser does not support a <wiggle> tag, it ignores the tag, and proceeds with what it knows how to do. If I were programming a new web browser, I might decide to add the functionality for the <wiggle> tag into my software.