Recommended events are events whose attributes are fully described in google analytics 4, but need further context to implement.
Recommended events are for common measurement scenarios that require additional context in order to be meaningful. If someone views one of your items, we want to tell Google Analytics about it. How does Google know which product was viewed and all of the important statistics around it. Because they require additional context, they are not automatically sent by the global site tag.
Google provides recommended events for ecommerce sites specifically. These events include product impressions measurement, events for payment, refund, promotions, events that are associated with the shopping cart, and more.
The below events are the ecommerce-related recommended events from Google: