A neural network has been trained to differentiate between popular and non-popular images and give like scores. This network was optimised to understand the features that made a photo popular on social media. Part of the work was inspired by Karpathy's blog on selfie (http://karpathy.github.io/2015/10/25/selfie/). However, our algorithm works on different type of images and not just selfies.

To add a bit to Parth's answer it has been trained using metric learning type losses and normal softmax combined. There is a next version of combined low/high level features combined algorithms we are slowly going to update into.