Italic text

HTML uses tags like <b>  and <i> for formatting output, like bold or italic text. These HTML tags are called formatting tags.

Use italic text to provide emphasis or contrast in text. The most common use for italics is to draw attention to a particular part of a text in order to show emphasis or contrast.

  • Use italics to denote titles.
  • Use italics for foreign words or phrases not considered fully part of the English language.
  • Apply italics when citing English words.

Difference between <i> and <em>

Using <i> doesn't say anything about why you want italics. It specifies only the presentation that you want.
In contrast, using <em> specifies a structural meaning. And it's easier for browsers or style sheet authors to use some other presentation for the structure when the typical default presentation is inappropriate.

<i> - Strictly a presentational element. If you want text to be italicized and not have any real semantic meaning, then wrap it in <i></i>
<em> - Strictly a structure element.
If you want text to be spoken with emphasis using a speech reader, then wrap it in <em></em>

Matt Cutts on <i> and <em>