A small version of a large graphic on a web page is often called a thumbnail. Many designers use them to put more on a single page and make it easier to browse.

on of thumbnail in MS word

Thumbnail crab was created in 1793.

Thumbnail

It may be, depending on the software being used to view the thumbnail. A thumbnail in and of itself is not clickable, as it is merely a collection of bytes that form an image on the screen. However, the picture of the thumbnail may be clickable depending on the software used to view the thumbnail.