What is cron job (cron job using popular web application)?

in unix OS ( from example ) when you need to run process using specific time and date

you need to put your process in cron job 

that help you to  Schedule your job

If your hosting provider doesn't allow setting cronjobs and you're looking for a simpler solution, you might consider a webcron services(like: https://www.easycron.com/) which will load a specific URL at a given time.