What is AIX and IRIX?

[Hektor]

What types of Unix systems are these? Are they old tecnology because I have never seen or heard of them until reading the description of this category.

I've heard of:
FreeBSD
HP-UX
Solaris

haha, for a long time I thought that "Unix" was just one operating system.

[Pan]

AIX - AIX is IBM's Unix implementation, which it develops for a number of its products, notably the IBM SP series. Other manufacturers, such as Motorola, also produce hardware that runs AIX. AIX incorporates elements of System V, BSD, and OSF/1, but includes enough unique features to make using, and especially administering, AIX somewhat different from working with other Unix implementations. Nevertheless, recent versions are compliant with most Unix standards.

IRIX - IRIX is a Unix implementation by Silicon Graphics. Though it incorporates its own extensions, IRIX is strongly System V-based and compliant to most Unix standards.

[Justice M]

I think that FreeBSD and Solaris are the two major Unix operating systems.
I would choose FreeBSD over Solaris; I had a Solaris server before and it didn't perform as well as my FreeBSD server.