RelayCommand is a design pattern commonly used in MVVM (Model-View-ViewModel) architecture, particularly in WPF (Windows Presentation Foundation) applications. It allows developers to define commands that can be bound to user interface elements, such as buttons. This enables a clear separation between the UI and the underlying logic, making the code more maintainable and testable. A RelayCommand typically implements the ICommand interface, which includes methods like Execute and CanExecute. The Execute method contains the logic to be executed when the command is invoked, while CanExecute determines whether the command can be executed based on certain conditions, enhancing user experience by enabling or disabling UI elements accordingly.