can anyone have basic idea of crontab in Linux?

Cron is an application that executes planned tasks at a defined time on Linux systems. The "crontab" (Cron Table) is a configuration file where these tasks can be added.
By working with a cron job (or scheduled task) you can execute recurring commands behind the scene's through the cron service, for example erasing cache folders, launching a backup script, synchronisation of files.
you better use commands such as
Modifying a crontab: crontab -e Displaying a crontab: crontab -l Removing all crontab entries: crontab -r this will definately help you in understanding crontab