The Emphasis element indicates typographic emphasis and is typically rendered in an italic font.

The <EM>Emphasis</EM> element typically renders as Italics.

would render :

The Emphasis element typically render as Italics.

<EM> can also take the CLASS, ID and STYLE attributes to allow style sheet definitions to be applied to it. For more details of these attributes, see the Style Sheets topic.

<CODE> Information and Character Formatting Elements Overview <KBD>