What is unix and linux?
Unix is an operating system that was developed at AT&T Bell laboratories by Ken Thompson and Dennis Ritchie in late 1960's. AT&t SVR5 introduced several commercial versions of Unix such as Sun Solaris, HP-UX(Hewlett-Packard), AIX(IBM), IRIX(Silicon Graphics) and many more variants.
Even Apple's OS-X is based on Unix derivative.
Linux is a free version of Unix that is available in the market. Main portion of Linux is Linux Kernel.
It can be either downloaded or can be purchased in packages from some of the companies like Red Hat, Suse, Ubuntu, CentOS, Debian.
It runs on Intel 486, Pentium processors.
More about Unix and Linux:
Unix is a multiuser operating system with some exceptions like DOS or Windows 3.1/95/98/ME. Resources include disk, processing time on CPU, memory, etc.
Linux can be used in embedded systems as well as it is considered a leading operating system on servers and big iron systems.