Using Ubuntu Linux/Glossary

Compiz: A compositing window manager.
X11: A bitmap system for displays. Developed by the X.Org Foundation.
Desktop environment: A graphical user interface paired with a set of software.
PulseAudio: Sound server software.
ALSA: Sound architecture.
Advanced Package Tool (APT): A package management system that originated in Debian (and was also used by Ubuntu since its early days).

See also