A command line interface (CLI) is a text-based user interface that allows users to interact with a computer's operating system or software by typing commands. Unlike graphical user interfaces (GUIs), which use visual elements like buttons and icons, CLIs require users to input specific text commands to perform tasks, such as navigating files or running programs. CLIs are commonly used by developers and system administrators because they can be more efficient for executing repetitive tasks and automating processes. Popular examples of CLIs include the Windows Command Prompt, Linux Terminal, and macOS Terminal, each providing a way to control the system through typed commands.