HyDE is an innovative zero-shot learning technique that combines GPT-3's language understanding with contrastive text encoders, revolutionizing information retrieval and grounding in real-world data. It generates hypothetical documents from queries and retrieves similar real-world documents, outperforming traditional unsupervised retrievers and rivaling fine-tuned retrievers across diverse tasks and languages. HyDE efficiently retrieves relevant real-world information without task-specific fine-tuning, broadening AI model applicability and effectiveness.