can anyone have basic idea of crontab in Linux?

The crontab is a list of commands that you want to run on a regular schedule, and also the name of the command used to manage that list. crontab stands for "cron table," because it uses the job scheduler cron to execute task. cron is the system process which will automatically perform tasks for you according to a set schedule. The schedule is called the crontab, which is also the name of the program used to edit that schedule. Technical Description crontab is the program used to edit, remove or list the tables used to drive the cron daemon. Each user can have their own crontab. Although these files are located in/var/spool/, they are not intended to be edited directly, and that's where the crontab command comes in. cron jobs can be allowed or disallowed for individual users, as specified in the files cron.allow and cron.deny, located in the directory /etc. If the cron.allow file exists, a user must be listed there in order to be allowed to use a given command. If the cron.allow file does not exist but the cron.deny file does, then a user must not be listed there in order to use a given command. If neither of these files exists, only the superuser will be allowed to use a given command. Another option is using PAM (pluggable authentication module) aunthentication to set up users who may or may not use crontab and system cron jobs, as configured in /etc/cron.d/.