Stands for "Advanced Interactive Executive," though some Linux fans have been known to refer to it as "Ain't UNIX." AIX is an operating system developed by IBM and is in fact Unix-based. It is typically used for enterprise servers and comes with a robust set of security options such as Kerberos V5 network authentication and dynamic secure tunnel authentication.
AIX allows the system administrator to divide memory, CPU, and disk access between various jobs. The OS supports IBM's 64-bit POWER processor and is backwards-compatible with 32-bit applications. It also runs most Linux applications (after recompiling them) and has full support for Java 2. If all that jargon makes no sense to you, relax -- AIX is not your typical consumer operating system. It is mainly used for servers in large businesses where IT geeks get to work with it.