Hotspots are plugin's for easily adding annotations, text, video, or other items to an image on the exact locations that you want.
Five important things that that can improve your website for Search Engines are:
JPG, GIF, TIFF, PNG, BMP. What are they, and how do you choose? These and many other file types are used to encode digital images. The choices are simpler than you might think.
Part of the reason for the plethora of file types is the need for compression. Image files can be quite large, and larger file types mean more disk usage and slower downloads. Compression is a term used to describe ways of cutting the size of the file. Compression schemes can by lossy or lossless.
Another reason for the many file types is that images differ in the number of colors they contain. If an image has few colors, a file type can be designed to exploit this as a way of reducing file size.