This is an Advertisment widget
A simple image is used here with some html tags that help to show text and description on it. You can view these html tags and how they are used in back-end at wp-admin-Widgets- Home Page After Content 2. The same way you can also show such image with the description on it. You can even use any other widget suitable here as per your requirement. you can follow the theme guide to know what else you can do with this theme.