BSD, which stands for "Berkeley Software Distribution," is a term used to describe an operating system that is derived from the original Unix operating system created at the University of California, Berkeley. Some synonymous terms include "BSD Unix" or simply "BSD," "Berkeley Unix," and "Berkeley Software." One of the most popular variants of BSD is FreeBSD, which is known for its robustness and reliability. Other notable variants include OpenBSD and NetBSD, both of which prioritize security and stability. While BSD is not as widely used as other operating systems like Windows or MacOS, it has a dedicated following and is highly respected in the world of computer science.