A Vehicle Drop is the act of reinforcing ground units with extra matériel. This can be done with transport helicopters, or vehicles dropped by transport planes via parachute. In Battlefield, this refers to one of several commander resources.
Added in patch 1.3, it is unique among resources because it can be requested by individual squad members, rather than just the squad leader.
The vehicle dropped is determined by the team (MEC and the PLA get the FAV or their teams light armored vehicle, while the USMC and EU get the DPV or HMMWV) and map size (sixteen version map sizes get buggies, while 32 and 64 versions get light armored vehicles). It's a good way to use it for squads who are long away without rides.
On Battlefield 2: Special Forces, vehicle drops on 16 player map variants get an ATV, while the 32/64 player versions get buggies.
Vehicle Drop is a commander resource in Battlefield 4 as a part of the squad asset loop that can be purchased by a Commander for four segments of the progression bar and then issued to squads. It deploys a single Quad Bike or Personal Watercraft (depending on the terrain) via parachute.