An image as defined by the w3c is an HTML object like an applet or an iframe which means that it is an independent object from the rest of the HTML document.
You can wrap an image with an anchor tag or by assigning an image map to it. With an image map you can create link targets on specific regions within an image. A start tag is required and the end tag is forbidden. For the most part you would use these image formats, jpg, .png, .gif.
If your creating an image map best practice is to use the longdesc attribute, this would provide all the image details to the search engines and user browsers. Essentially what the IMG element does is embed an image in your HTML document, your job in SEO is to use the attributes available to assign descriptive meta data.
Image SEO Basics
After adding the usual alt and title tags to your Images make sure to include relevant text around the vicinity of the image that’ll match what the image is about.
Text related to the image below
Whenever possible try to save your images in the GIF format. You can significantly reduce server load by using GIFs instead of JPGs.