Question: Whenever we use man command it opens the manual corresponding to the command(if exists). Operations on it are almost same as that of the less command(like search forward using / or backward using ? or browse forward using d etc). I am just curious whether man command internally invokes less command to display the manual contents?

Answer: 
By default, yes. This can be overridden via `$PAGER` and `$MANPAGER` in turn.
I would like to complement Ignacio's accepted answer.

Even the man utility has a [manual](http://man7.org/linux/man-pages/man1/man.1.html) that can be displayed by the man utility: **man man**.

The part answering your question:

> 
> Controlling formatted output
> 
> 
> 
> ```
>    -P pager, --pager=pager
>           Specify which output pager to use.  By default, man uses less
>           -s.  This option overrides the $MANPAGER environment variable,
>           which in turn overrides the $PAGER environment variable.  It
>           is not used in conjunction with -f or -k.
> 
> ```
> 
>