I entered the man manual page but i did not know that how to use the -H and -X flag along with man. The following has written in the man manual page
-H[browser], --html[=browser]This option will cause groff to produce HTML output, and will display that output in a web browser. The choice of browser is determined by the optional browser argument ifone is provided, by the $BROWSER environment variable, or by a compile-time default if that is unset (usually lynx). This option implies -t, and will only work with GNUtroff.
And the following is written for the -X flag in man manual page
-X[dpi], --gxditview[=dpi]This option displays the output of groff in a graphical window using the gxditview program. The dpi (dots per inch) may be 75, 75-12, 100, or 100-12, defaulting to 75; the-12 variants use a 12-point base font. This option implies -T with the X75, X75-12, X100, or X100-12 device respectively.
an also could you guys explain the groff and troff and what is the difference between both and which one is right?