User Interface (UI) is the component of the computer system through which the user interacts.

Command Line Interface (CLI) presents a prompt where users input commands for execution. In CLI environments, programs dictate the sequence of events. Users are constrained to input data in the specific order requested by the program.

Graphical User Interface (GUI) facilitates user interaction with software via graphical elements displayed on the screen. In a GUI environment, events are driven by user actions. Users dictate the sequence of events by initiating actions. Users trigger events, and the program responds accordingly to those events.