What is command and syntax of command line?

Command is a program that tells the UNIX system to do something. It has the form:
command [options][arguments]
Where an argument indicates on what command is to perform actions, usually  a file or set of files. An option modifies the command and changing the way it perform.
Option are generally precede by hyphen (-), and for most commands, more than one option can be stung together, in the form :
command -[option][option][option]