cliclick is short for "Command-Line Interface Click". It is a a tiny shell / Terminal application that will emulate mouse and/or keyboard events such as moving the mouse, clicking, double-clicking, dragging with or without modifier keys, or typing text.
Hence, it is a tool for automating/scripting things that cannot otherwise be scripted (for instance, using AppleScript). Other than GUI Scripting, it does not require "Access for assistive devices" to be activated in the System Preferences.