Call a process - Documentation Clarification

The entire documentation for this step type is:

Call a process
This step type allows you to invoke another process within the same application. You can pass data to the process being invoked using literal values or expressions.

I need more explanations what the following mean: ‘Add or lookup process input?’

  1. Add: A new record will be created using the data you supply. If another record exists with the same primary key, that record will be updated and used.
    a. Where will this record be created? You never reference table?
    b. What about returned results? How do you use those variables as input?

  2. Lookup: The record will be retrieved using the primary key. Any additional columns will be used to update the record.
    a. Primary key from where and to where?
    b. What happens to columns which you don’t specify?

I think you are talking about this?

This thread would probably be better served in the #appsheet-automation channel.

The Process that you are calling will be attached to a Table.

Don’t know. This part may still be a work-in-progress.

The primary key of the record that you are looking up, from the table that the Process you are calling is attached to.