Schedule Actions add-on adds the ability to schedule any action to force it’s execution after a time delay or a specific date of your choice!
For example, You can set up an automation like “When user purchases a product, send an email 7 days after” or “When user completes a course, Send an email on Dec 31th at 08:00 AM“.
Schedule Actions add-on works with all actions supported by AutomatorWP and you can find a full guide about how this add-on works on the schedule actions of an automation page.
Also, Schedule Actions add-on makes use of the WP Cron functionality (with built-in support for Action Scheduler) and this page explains it in depth.
Also, you can check the automations samples page where you can see some samples of the possibilities of this add-on.