Explanation
Graphical user interface, text, application Description automatically generated

Box 1: PreValidation
For the initial operation, this stage will occur before the main system operation.
This provides an opportunity to include logic to cancel the operation before the database transaction.
Box 2: PreOperation
Occurs before the main system operation and within the database transaction.
If you want to change any values for an entity included in the message, you should do it here.
Avoid cancelling an operation here. Canceling will trigger a rollback of the transaction and have significant performance impact.
Box 3: PostOperation
Occurs after the main system operation and within the database transaction.
Use this stage to modify any properties of the message before it is returned to the caller.
Reference:
https://docs.microsoft.com/en-us/powerapps/developer/data-platform/event-framework