UI components are the building blocks of user interfaces in software applications. They include elements like buttons, text fields, sliders, and menus that users interact with. Each component serves a specific function, helping to create a seamless experience for users as they navigate through an application or website. These components are often designed to be reusable, allowing developers to maintain consistency across different parts of an application. Frameworks like React and Angular provide libraries of pre-built UI components, making it easier for developers to create visually appealing and functional interfaces without starting from scratch.