The DROP is a Heliconcept specialised for Heliboarding.
Coaxial rotors are a pair of helicopter rotors mounted one above the other on concentric shafts, with the same axis of rotation, but that turn in opposite directions.
One benefit arising from a coaxial design include increased payload for the same engine power - a tail rotor typically wastes some of the power that would otherwise be devoted to lift and thrust, whereas with a coaxial rotor design, all of the available engine power is devoted to lift and thrust. Also, helicopters using coaxial rotors tend to be more compact (occupying a smaller 'footprint' on the ground), though at the price of increased height, and consequently have uses in areas where space is at a premium.