MVVM Light is a lightweight framework designed to simplify the development of applications using the MVVM (Model-View-ViewModel) architectural pattern. It provides essential tools and components that help developers separate the user interface from the business logic, making applications easier to manage and test. The framework includes features like RelayCommand for handling user interactions and Messenger for communication between different parts of the application. By using MVVM Light, developers can create more maintainable and scalable applications, particularly in environments like WPF (Windows Presentation Foundation) and Xamarin.