How to add notifications to website based on database change?

I am creating website for fastfood ordering. How can i alert a personal, that someone made an offer on website? I have created web where customer can make offer and other site for administration. Both connected to database. What i need is to give notification, alert any beep or anything for admin, when customer make offer and add row to table in database.

I found this enter image description here

but i dont know how to execute notification when database is changed. How to check it.