Daemon A program that runs in the background, and stays running all the time, providing utilities for other programs or waiting for a request from the Internet or a local network.
Desktop Environment Name for the set of programs responsible for displaying the desktop in an operating system, its icons, taskbar, start menu, or equivalents.
Distro Abbreviation of "distribution," and typically refers to an operating system distributed (i.e. that can be installed) based on Linux, or, in some cases, on BSD.