The file access permissions is a combination of letters and hyphens. The letters and hyphens will make up 10 total symbols. The letters are d, r, w, x and occasionally s or S.
In a Unix system, the two fundamental notion is that things are either a file or a process. A file is just a destination for or a source of a stream of data. A process on the other hand is a program that is currently running and this program may be associated with a file that either stores the instructions that the program runs or a file that stores the output that the program generates.