The crontab is a list of commands to be executed in the scheduled manner, and also the name of the command is used to manage that list. crontab stands for “cron table,” because it uses the job scheduler cron to execute tasks. The crontab command is used to edit your crontab file. It creates a crontab file containing commands and also instructions for the cron daemon to execute. The Linux crontab documentation is pretty clear about editing the crontab files. Each user can have their own crontab, and though these are files in /var/spool, they are not intended to be edited directly.
Command to edit cronjob as root user