Visudo

[bam]

do I have to use this to edit sudoers file or can I use something else. If I have to use it, then why, whats the reason behind this?

[kbranch]

I think that's the preferred way to do it, but I always use a plain text editor.  Make sure you know what you're doing, of course.

[speculatrix]

visudo will verify that the sudoers file is syntactically correct when you have finished.
editing it manually is possible BUT you can end up leaving it half broken.

moral: make a backup before you start!