Flow Content vs. Phrasing Content

Within the body section of an HTML document, most non-empty HTML elements that do not expect content consisting of specific child elements will expect one of two different categories of content:

flow content

The body element, which is the beginning of the visible content of the document, expects content that consists of flow content. Flow content is less restrictive than phrasing content because sectioning tags, heading and footer tags as well as text and the HTML tags that can be used in phrasing content can be used where flow content is permitted.

phrasing content

Phrasing content is the content at the lower level that consists of text and HTML elements that mark up the text within paragraphs. Phrasing content is more restrictive than flow content, since there are many tags, such as block tags, that are not permitted in phrasing content.

Some tags that appear similar at first glance may expect different content models. For example, considering the two types of child elements of the dl element:

• the inner HTML of a dd element for a definition description can be any flow content, but
• the inner HTML of a dt element for a definition term is restricted to phrasing content only

Therefore, a dt element in a definition list should not contain any block tags such as a <p> paragraph tag or <hr/> tag.