Rec-a-Sketch was created by Ethan Rosenthal and is an interactive website to help people discover content on Sketchfab. There are 3 types of recommendation algorithms that recommend other models to view based on their similarity to the input model. The following blog posts outline how each algorithm works:
Clicking on the images of the recommended models takes you to new recommendations. Clicking on the text under the model links out to their Sketchfab page.
For information on how the data was collected, see this blog post.
To see the code behind this website and the data collection, check out this github repo.