Cron is a time-based job scheduler in Unix-like operating systems, which is used to automate repetitive tasks. It is a daemon (a background process) that runs continuously and executes commands at specified times, called cronjobs. A cronjob can be any command, script or program that needs to be executed at a specific time or interval.
The crontab is a file used by cron to schedule the execution of cronjobs. Each user on the system has their own crontab file, which is stored in the /var/spool/cron directory. The crontab file contains the instructions for the cron daemon on when to run a command, and what command to run. The syntax for the crontab file can seem a bit confusing at first, but it’s actually quite simple once you understand the structure.