Explanation:

Box 1: Autonumber column
Autonumber columns are columns that automatically generate alphanumeric strings whenever they are created.
Box 2: Business rule
By combining conditions and actions, you can do any of the following with business rules:
* Enable or disable columns
* Set column values
* Clear column values
* Set column requirement levels
* Show or hide columns
* Validate data and show error messages
* Create business recommendations based on business intelligence.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/autonumber-fields
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/data-platform-create-business-rule