pipe is used to direct the output of a set of commands to 
another set of commands meaning output of one will be fed 
as input to the other
tee is used to display the output on the screen

pipe is used to execute two or more commands 
eg:select ename||'works as '||job from emp;

tee is used to create an empty file,stores the output and 
then displays the contents on the screen
eg: grep "^d" filename||tee file

seperate arguments

'|' --> This will take output and send it as the input for 
next command

tee --> tee will generate two outputs

A Pipe would allow you to direct output of one command  to 
the input of another command ie. directs a stream from one 
file to another.

A Tee command does the same job of directing streams 
however it directs the stream to two destinations direction 
one is the direction where the stream would otherwise end 
up if there was no Tee command And the other direction is 
the file that is argument to Tee command.

So, A Tee is used in Pipes to direct streams to an outside  
file without interrupting the regular propagation of stream 
in the pipe.
  eg. 

                  Pipe
  ----------------------------------------
Output of A                           Input of B
  ----------------------------------------


                  Pipe
  ----------------------------------------
Output of A    ========               Input of B
  ----------------||----------------------
                  ||
                  ||
             Input of C

seperate arguments