ALT attribute is designed to be an alternative text description for images. ALT text displays before the image is loaded (if it's loaded at all) in the major browsers and instead of the image in text-based browsers like Lynx. ALT is a required element for images and can only be used for image tags because its specific purpose is to describe images.

<img src="cafeteria.jpg" height="200" width="200" alt="UAHC campers enjoy a meal in the camp cafeteria">

ALT describes the image (a photo of the camp cafeteria).