Most quality tool manufacturers have adopted a common battery strategy in recent years. Having a common battery for several tools can save the owner money, as rechargeable batteries are expensive. It also protects the owner from damaging tools by installing an incorrect battery.
The P202 is a compact cordless drill and driver. It is part of the 18V ONE+ line of tools. It has a heavy duty 1/2-inch chuck. It also has a two speed gearbox and a 24 position clutch making it useful for many applications. The drill is also equipped with a built-in magnetic tray to keep screws or bits handy and bubble level to help the user drill level holes.
The P815 drill kit contains the P202 drill, two compact lithium-ion batteries, a charger and a tool bag designed to hold the entire kit. The charger is a "dual chemistry charger," designed to support lithium-ion and nickel-cadmium batteries.
For someone who owns other tools in the 18V ONE+ family, the bare P202 drill might be the best purchase. The P202 drill is available without battery or charger from several online retailers. If this is the start of a tool collection, the kit is a better buy, as it contains the needed batteries and chargers.