SQuAD 2.0 (Stanford Question Answering Dataset) is a dataset created by researchers at Stanford University in 2018 and is considered one of the most widely used in this domain, with over 100,000 questions and answers drawn from more than 500 Wikipedia articles. It's used in natural language processing and machine learning research for question-answering tasks. Unlike its predecessor, SQuAD 1.0, released in 2016, SQuAD 2.0 features challenging questions that require reasoning and reading comprehension, and it also includes unanswerable questions. SQuAD 2.0 is annotated by human annotators and provides multiple plausible answers for each question. It's focused on generalization, making it suitable for evaluating various approaches to question answering.