The main purpose of the shell is to run commands and programs. UNIX commands and programs generally take the following syntax:
command options parameters
The command is the name of the file as it appears in the directory. The options generally change the way the command will function and will usually consist of single letters preceded by a minus sign. The parameters could be anything, such as filenames or user names.
All commands have a name (otherwise they would not exist), but they don't all take options and they don't all take parameters. Even those that do take options and/or parameters (which is most) don't always have to be supplied with them. (The Solaris man pages give the usage of all Solaris commands. It is recommended ...