Open-domain refers to a type of system or application that can engage with a wide range of topics without being limited to a specific subject area. This means that the system can answer questions or provide information on various subjects, such as science, history, or pop culture, making it versatile and user-friendly. In the context of artificial intelligence, open-domain systems are designed to understand and generate responses based on diverse inputs. For example, a chatbot operating in an open-domain setting can handle inquiries about anything from weather forecasts to movie recommendations, showcasing its ability to adapt to different conversational topics.