The NuGet CLI (Command Line Interface) is a tool used for managing NuGet packages in .NET projects. It allows developers to install, update, and remove packages directly from the command line, making it easier to automate tasks and integrate with build processes. With the NuGet CLI, users can create their own packages, push them to a NuGet repository, and restore packages for their projects. This tool is essential for maintaining dependencies and ensuring that projects have the necessary libraries to function correctly, streamlining the development workflow.