Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration. Unix systems are characterized by various concepts: the use of plain text for storing data; a hierarchical file system; treating devices and certain types of inter-process communication (IPC) as files; and the use of a large number of software tools, small programs that can be strung together through a command line interpreter using pipes, as opposed to using a single monolithic program that includes all of the same functionality. These concepts are known as the Unix philosophy.
Unix, which is not an acronym, was developed by some of the members of the Multics team at the bell labs starting in the late 1960's by many of the same people who helped create the C programming language. The Unix today, however, is not just the work of a couple of programmers. Many other organizations, institutes and various other individuals contributed significant additions to the system we now know today.