"green" linux user needs CRON clarification

["William Schwartz" <willschwartz@usa.net>]

OK, I've been having problems understanding something. I'm new to debian,
and I still cant figure this out about cron... I have read the man pages,
but I'm still not clear.

There is a filed called "crontab" in the "etc" directory. That is my "system
wide" crontab. This file I am able to edit and modify...

then there are crontab files in the "/var/spool/cron/crontabs" directory
that are to be edited with the crontab command...

The "crontab" file in the "etc" directory has a parameter called "user". and
I use it to specify "root" because I need to schedule a job as root...

I guess my question is: what is the difference between the two? and which
one should I use? I need a program to run every 5 minutes to do some
polling. and I want it to happen 24/7.

Thanks!
Will