A NuGet Package is a single file that contains compiled code, resources, and metadata used in software development, particularly for applications built on the Microsoft .NET platform. It simplifies the process of sharing and reusing code by allowing developers to easily add, update, or remove libraries in their projects. These packages are stored in a central repository called the NuGet Gallery, where developers can publish their own packages or download existing ones. Using NuGet Package Manager, developers can manage dependencies and ensure their applications have the necessary components to function correctly.