HTML

Files that have the file extension "html" are expected to contain a description of a Web page using a notation called hypertext markup language. This language describes the page layout in functional roles, and leaves the exact layout up to the browser. For example the following part of an "html" file says that the characters between the <p> and the </p> are to be formatted as a paragraph, but exactly how the paragraph is laid out is up to the browser.

<p>
It began one day in
summer about thirty years ago,
and it happened to four children.
Jane was the oldest 
and Mark was the only boy, 
and between them they ran everything.
</p>

Here is what your current Web browser does for that paragraph:

It began one day in summer about thirty years ago, and it happened to four children. Jane was the oldest and Mark was the only boy, and between them they ran everything.

The <p> and </p> are examples of HTML tags that describe the layout of a page. Often tags come in matched pairs that are used to show the start and end of something. If tag like <something> has a matching tag, the matching tag will look like </something> . The "markup" of the phrase hypertext markup language means that you describe the functional role of each part of the file, but the browser decides how to implement that role. For example, the functional role of the text between <p> and </p> is that of a paragraph.