Both are central air conditioning systems.
A single-package a/c combines the unit’s condense and air handling in a single casing. If your air conditioner sits on your roof, it’s probably a single-package system.
A split system separates the two functions, so the evaporator is indoors and the condenser unit is outside.
To qualify for the new federal tax credit for energy efficiency, a rooftop unit needs a SEER of 14 or higher and an EER of at least 12. A split-system unit must have a SEER of 16 or more and an EER of no less than 13. You can claim the tax credit on 30 percent of the price of your new, energy-efficient air conditioning, including installation, up to $1,500.