System class  belongs to java.lang package.It provides platform independent
resources such as the standard input,output and error streams.All methods and
variables in system  class are public and static.due to this the class need not
be instantiated.

This java.lang package contains predefined input,output streams.

the basic printing methods are from printstream class.it provides references to
a printstream object that can access those methods

The out variable  is a member of the System class.

Since it is a Static variable to retrieve a reference to the out variable u have
to use the syntax

System.out.