Perplexity Copilot is a digital assistant for in-depth question answering. It is based on advanced AI models such as GPT-4 and Claude 2, and differs from conventional search engines in its ability to engage in dialog, ask clarifying questions, and select the most relevant information from a variety of sources. Copilot is used in academic and professional research, as well as for writing news summaries. The system allows users of the free plan to make five queries every four hours, and subscribers can make more than 600 queries per day.