The “auto-population fields” option can be used to pull in data from another record when using record links. This can be used to increase data capture speed in the field by automatically pulling in data that you wish to populate in fields from the other app.
When setting the auto-populate field option, you will be able to select what field you would like to pull values from in the linked record (left column) and what field you will like to populate with those values (right column).
NOTE: You will not be able to use auto-populate fields if you have the allow multiple records option enabled.
In the example above, the value contained within the "Store Number" field in the linked app is being populated into the "Store Number (store_number)" field in the app with the record link field.