A catalog is a systematic list or collection of items, often organized for easy reference. It can include products, services, or resources, and is commonly used in libraries, stores, and online platforms. Catalogs help users find specific items quickly and efficiently. In a library, for example, a catalog may include books, journals, and multimedia resources, allowing patrons to search by title, author, or subject. Similarly, an online store's catalog displays available products, often with descriptions and prices, making it easier for customers to browse and make purchases.