Unix is an operating system with features like portability, multi-user access, and multi-tasking. It uses a hierarchical file structure and has over 200 utility programs. The three main components of Unix architecture are application programs, the kernel, and the shell. The kernel interfaces with hardware and manages tasks like memory, processes, and file management. The shell acts as an interface between the user and kernel and uses standard syntax for commands. Files and directories are organized in a tree structure in the file system.