"Your covered auto" includes the vehicles listed in the declarations, a newly acquired auto, and a temporary substitute. A temporary substitute is a non-owned vehicle used while the listed auto is out of normal use because of breakdown, repair, servicing, loss or destruction. Borrowing a friend's car for convenience while your own car is usable does not qualify.
Newly acquired auto: it receives the broadest coverage provided for any vehicle shown in the declarations, except for collision coverage for damage to the auto, which has its own rule. So if one listed car carries higher limits than another, the new car gets the higher limits, not the state minimum.
Collision on a newly acquired auto (CDI outline):
If at least one auto in the declarations has collision, all coverage on the new auto begins on the date the insured becomes the owner. The ISO policy requires the insured to notify the insurer within 14 days. The notice can come after a loss, as long as it is on time.
If no listed auto has collision, collision on the new auto can still begin on the date the insured becomes the owner, but the insured must request it.
Vacation rental: a private passenger car the named insured rents on a short vacation is a non-owned auto. Liability follows the named insured, and the physical damage coverage carried on the insured's own car extends to the rental. No advance notice is required, and declining the rental company's options does not take away the PAP coverage.