What effect does the <em> tag have on text?

The tag is used in HTML to provide emphasis on text. This emphasis typically manifests in a visual style change, most commonly rendering the text in italics, which helps to convey a stronger meaning or importance. When content is marked up with the tag, it signifies to both browsers and assistive technologies that this particular text should be regarded with special significance compared to the surrounding text. This is particularly important for accessibility, as it allows users to understand the importance of the emphasized content. Thus, the correct answer reflects the primary purpose of the tag, which is to emphasize text in a way that enriches its meaning within the context of the content.