Perplexity AI is a free AI-powered search engine that provides users with accurate, cited answers to their questions. It leverages large language models (LLMs) and sources information from the web, offering a conversational and verifiable search experience. The engine is available as a website, mobile apps (Android and iOS), and a Chrome extension. Perplexity AI also offers a paid enterprise version for businesses. Marketing materials highlight its speed, accuracy, and integration of AI technologies like ChatGPT and GPT-4.