Putting basic link tags around an image makes the entire image a link. Alternatively, an image map, created by web pioneer Kevin Hughes in 1993, allows for multiple links at predefined areas within an image.
Back then, you had to use server-side programming to get image maps to work.
Eventually, though, the browser vendors programmed the browser to handle the workload—as long as the HTML contained a map that specified the coordinates of the links within the image.
Today, for simplicity and accessibility, server-side image maps are the only ones still used.