Fields in PWR apps represents what the columns represent in relational databases. It can store data values which are required for a particular object in a record. Fields can store many different types of data.
There are 3 types of fields:
(A) Standard Field:
There is one standard field in every Custom object and the field get created at the time of creation of object. This is cannot be deleted or edited.
For Standard object, the fields which are present by default in them, cannot be deleted from standard object.
(B) Custom Field:
Custom fields can be create on Standard or Custom object. They may or may not be required.
...
A formula field can reference the value of another custom or standard field using a merge field.
(C) Audit Field:
Record Id:
A Record ID can help you identify a record in the database. Each record in system has a unique ID field assigned to it which is known as Record ID. It is system generated and cannot be edited or deleted. It is generated every time a new record is inserted into the application.
...
The date and timestamp for changes made to an individual record, including the User who made the change. Unfortunately you won't be able to change the "last modified by" field, as this is a system field that is read only.
Deleted By:
Deleted by field is a built-in (non-custom) audit field is used to record which syncing user deleted a record.
Deleted On:
Deleted by is a field where date refers to the last time a document or file was deleted.
Last Modified On:
The "Last Modified On" date refers to the last time a document or media file was modified. This information is gathered from metadata within the document or from the website's servers.
Is Test Record:
The field “Is Test Record” is used by the developer to maintain the test record.
Is Deleted:
Erase On:
When any of the record has been deleted from the org its gets reflected in the Erase On field. The restore limit for the Erase On field is of 30 days.
Is Published:
Once you publish an object, you can select which individual fields on that object are published. For standard objects that are published, a default set of fields is automatically published.
...