This app allows students to drag labels and drop them into frames, indicating the different parts of an image. This image can be a screenshot of any lab, a diagram explaining the different components of something, etc. 

After uploading the image, the teacher adds the labels and specifies the locations of the corresponding frames. The teacher can also, optionally, add details (description or question) to these labels. After the students fill the frames and check that they have answered correctly, they will be able to view the additional information or answer the questions, if any.

To learn more about how to configure the app, visit the Support Page's section on How to set up Apps, or use this direct link.