What is the <em> tag used for in HTML?

The <em> (Emphasis) tag in HTML is used to highlight a fragment of text with an emphasis, indicating its increased importance or emotional tone. Browsers typically display the text inside <em> in italics, but the main purpose of the tag is semantic — it informs search engines and assistive technologies (such as screen readers) that this text should be perceived with special emphasis.

Example of usage:

<p>This text is normal, and <em>this one</em> is emphasized.</p>