Pretty wide aperature on that.

1. You cannot log something fraudulently, and then use it for any official FAA purpose (ie aeronautical experience for cert, rating, privilege, profiency, etc). I don't think there's any legal proscription on lying to employers, although I'm obviously not recommending it.

2. You must log enough info to show you meet FAA currency for any operations which you conduct (night landings, instrument operations, etc).

Other than that you have very wide discretion on what, when and how to log stuff. Employers obviously like the usual formats found in off-the-shelf logbooks, or similar.