What is a Cron Job

A Cron Job is a task that should be executed repetitively at regular intervals. It is an action that only your server is capable of scheduling.

Example: the website weekly-backup that most hosting companies offers to their clients, is a classic example of a Cron Job. The server has scheduled the backup operation on, for example, every Saturday night at 00:00.

Crons consist of a server-command that is executed at regular intervals: every day, every month, every Saturday, at midnight, every 10 minutes, every hour etc.. In order to set up such repetitively actions, your server requires a 'Cron Utility' to be installed. One of the most popular Cron Utility for Linux Severs is crontab.

If your server has a Control Panel, then you should check if a feature called 'Cron Jobs' exists. You should ask your hosting company if your server supports any Cron utility to schedule Jobs.
Once you know whether your server supports such functions, you just need to find the command that the server should execute at regular intervals.

VikAppointments comes with several pre-installed cron jobs. Once you will have configured any of those crons, the system will automatically start running them thanks to the WP-Cron feature.

Any tasks scheduled to be run will be executed during that page load. Since this is not a real cron, it does not run constantly as a system cron does; it is only triggered on page load when a user visit your website. In case someone doesn't visit the page during the schedule of a procedure, the cron won't be executed.
In order to prevent this behavior, it is needed to setup a server cron job to periodically hit the website and simulate a user's visit.