Problem with Cron

I am trying to schedule a command with the help of crontab. I edited
and installed the crontab using the cmd `crontab -e`. By running the
cmd `crontab -l` I am able to see the crontab listing for that user.
But the cron does not execute the command at all. I do not find any
entry in the /var/log/cron file for the cmd. What am i missing ? I
found the following statement in the man pages of cron "Cron searches
/var/spool/cron for crontab files which are named after accounts in
/etc/passwd; crontabs found are loaded into memory." How are these
files created ? Are they created when I install crontab ?
Please clarify my doubt ?:confused:
Thankx in advance,