Custom controls are user interface elements that developers create to meet specific needs in software applications. Unlike standard controls, such as buttons or sliders, custom controls can be tailored in appearance and functionality, allowing for a unique user experience. They are often built using programming frameworks like React or Angular. These controls can encapsulate complex behaviors and styles, making them reusable across different parts of an application. By using custom controls, developers can enhance usability and maintain consistency in design, ultimately improving the overall performance and aesthetics of the software.