"The Dropship is a two-engine VTOL craft that combines advances in shielded hardware, redundant software protocols, and networked aeronautics into a heavily armoured tactical platform capable of insertion and extraction in even the most hostile situations. Its standard five-man carrying capacity, dual hard-points, and reinforced plating allow it to operate independently in any situation, alternately tracking and engaging enemy targets and ferrying troops into and out of harm's way."
The dropship's primary function is as a high speed troop carrier. A normal dropship is able to deploy a whole squad (excluding the pilot) at high speed and altitude (assault variants can only deploy four people excluding the pilot) it can also loiter to provide fire support (particularly deadly for assault variants), or be a mobile CRU carrier to act as an anchoring unit for a beachhead.
Assault dropships are very effective against HAVs, as they can hover above it (where the gun can't aim at them), and slowly chip away their health. They hold a similar devastating effect against infantry in open ground.
List may be out of date.