What is meant by contrastive learning objective?

[majdsalman]

Having read the paper and the code I don't understand what is meant by "These judges are lightweight models fine-tuned against a contrastive learning objective.".

The loss function is a cross entropy loss and the task is a classification task (yes/no) for belonging or not belonging in a class. There is no notion in the code of maximizing the separation of these classes in the embeddings space. The phrasing adds some confusion since contrastive typically means something else.