The FARs define that pretty well. But their interest is in certs, rating, and currency. There are a few grey areas as far as logging experience for employers but even most of those have been resolved by FAA legal interpretations.

Employers are pretty good at parsing the few grey areas, they will have you fill out their apps in a specific manner. Your logbook does not need to mirror employer apps in every way, but you will need to be able to how you got from A in your book to B on their app.

Defining a standard time-logging scheme for employer convenience isn't really a business the FAA wants to be in. They only got involved with PRIA and then PRD because congress made them do it.