From http://www.w3schools.com (Copyright Refsnes Data)

SMIL Files

A SMIL file describes a multimedia presentation.

A SMIL file contains all the information necessary to describe a multimedia presentation.

SMIL files are stored with the file extension *.smil

A SMIL file contains the following:

SMIL Markup

Since SMIL is based on XML, the tags are case sensitive. All SMIL tags requires lowercase letters.

A SMIL document must start with a <smil> tag and end with a </smil> closing tag. It may contain a <head> element and must contain a <body> element.

The <head> element is used to store information about the presentation layout and other meta information.

The <body> element contains the media elements.

<smil>
<body>
  <seq repeatCount="indefinite">
    <img src="image1.jpg" dur="3s" />
    <img src="image2.jpg" dur="3s" />
  </seq>
</body>
</smil>

To play a SMIL presentation, you will need a SMIL player. Different SMIL players can be found on the Internet:

With Internet Explorer 5.5 or later, SMIL elements can be inserted into HTML files.

This way any SMIL presentation can run over the Internet as standard HTML files.

The rest of this tutorial will use Internet Explorer 5.5 or later to demonstrate the use of the different SMIL elements.