External style sheets should be used to set the overall styles for multiple pages of a web site. The style rules are defined on a separate file and attached to the pages of the site that use those styles.
Embedded style sheets should be used to set the style rules for a single page. The style rules are defined within the heading of the document between style tags.
Inline style sheets are defined on the individual tag as an attribute. They are used to add style to a single tag, or override a higher level style rule. The range of the inline style ends with the tag is applied to.