The document discusses weak supervision, which uses unreliable labels to train machine learning models. Weak supervision works by creating many labeling functions that assign probabilistic labels to data, rather than definitive labels. These functions can be rules, user reviews, model predictions, and other heuristics. A generative model then learns the accuracy of labeling functions to determine the true labels. This technique can achieve good results with only a small number of true labels. However, it is difficult to evaluate and influence the importance of labeling functions without labels. The document promotes creating many diverse labeling functions to take advantage of weak supervision.