What tag is used to mark up an image in a webpage?

The "img" tag is used to embed images in a webpage, making it integral to HTML coding. This tag allows developers to display images and requires an "src" attribute that tells the browser where to find the image file. Additionally, the "alt" attribute can be included to provide alternate text that describes the image, enhancing accessibility for users who rely on screen readers.

Unlike the "figure" tag, which is utilized to encapsulate images and their captions, the "img" tag is specifically designed for inserting the image itself into the document. The "map" tag is used to define an image map for client-side image maps, linking different areas of an image to different destinations, and the "photo" tag does not exist in HTML and is not a standard way to mark up images. Thus, the "img" tag stands out as the correct choice for marking up images on a webpage.