Key on keyless remote
I have a 2012 Infiniti G37 (also made by Nissan Motor Corp)..This key which detaches from your keyfob will allow you to open the door and possibly access the trunk, if your keyfob battery dies. I think your Altima is similar to my Infiniti with the push button start..so while you may NOT need to insert the key itself, you will likely need to insert into a 'keyfob port" to allow you to start the car if the battery dies (my Infiniti works this way). Get extra batteries for your fob and keep 'em around, just in case.
Also, you can unlock and lock the glovebox with the key. Why are you asking about the key???
Looking for a Used Altima in your area?
CarGurus has 87,467 nationwide Altima listings starting at $1,095.
Search Nissan Altima Questions
Nissan Altima Experts