CLI tools, or Command Line Interface tools, are software programs that allow users to interact with their computer's operating system through text-based commands. Instead of using a graphical user interface (GUI) with buttons and menus, users type commands into a terminal or command prompt to perform tasks like file management, system monitoring, and software installation. These tools are often favored by developers and system administrators for their speed and efficiency. Popular CLI tools include Git for version control, curl for transferring data, and grep for searching text. Mastering CLI tools can enhance productivity and streamline workflows.