The document discusses different types of backgrounds that can be used in HTML including background color, background picture, and background sound. It provides the syntax and steps to insert each type of background. For background color, the <body> tag uses the bgcolor attribute. For background picture, the <body> tag uses the background attribute along with the image URL. For background sound, the <bgsound> tag is used along with the src attribute and sound URL. The document also explains how to get the URL for images and sounds to use in the background.