Open-Domain Question Answering (ODQA) is a field in artificial intelligence focused on developing systems that can answer questions posed in natural language. Unlike closed-domain systems, which are limited to specific topics, ODQA systems can retrieve information from a wide range of sources, including web pages, databases, and documents. These systems utilize various techniques, such as natural language processing and machine learning, to understand the question and find relevant answers. ODQA is used in applications like virtual assistants and search engines, enabling users to obtain information quickly and efficiently without needing to specify a particular domain.