Highlighting a fragment of the picture.

Habralyudi, cry for help. In that year, there was an article on Habré on how to correctly implement the following task: There is a picture, when you hover over a certain area, it (the region) should change (and the balloon pops up with a tag, but this is not the point). If someone has it left in the bookmarks, or someone saw something similar, I beg you to help. Thank you all =)