AI refers to building systems that can perform intelligent tasks, while machine learning (ML) refers to systems that can learn from experience. Natural language processing (NLP) involves systems that can understand human language. There are three main types of machine learning: supervised learning uses human-annotated data to train models, semi-supervised learning uses a small amount of annotated data and a large amount of unannotated data, and unsupervised learning uses only unannotated data. The Atticus Project is open-sourcing a labeled legal contracts dataset to improve the accuracy of AI-based contract review tools, where "labeled" means volunteers have marked relevant legal provisions under attorney supervision.