Summary
In Halo 1, the Covenant dropships are angular, tuning fork shaped craft with personnel bays along the exterior of each "prong". Although not named by Bungie, these vehicles are sometimes called "Apparitions," "Bandits," or "U-shape" by fans. It is also interesting to note that in a mod for Command and Conquer Generals by Slipstream Productions, they are called "Harbingers"
A marine in the level "Halo" called one of these a "Bandit". But this is a military term used for any form of enemy.
Between the extended personnel bays, and energy field fluctuates visibly as it generates the ship's antigravity propulsion (similar in appearance to the energy pulse of the "Gravity Lift" elevators the Covenant use to commute between the ground and the hovering ships). This same gravity-beam is used to ferry Ghosts and light ground vehicles to their destinations. In addition to the pilot, the ship is crewed by a single gunner for the underslung bubble-shaped plasma gun turret--similar to the Shade but with a higher rate of fire. Each troop bay can hold four fully equipped Covenant warriors.
According to the book Halo: First Strike, these dropships also have life support for use in vacuum. Contrary to some people's beliefs, they do not have a Slipspace drive, in First Strike, it was dumped out of a ship already in Slipspace, with ample modifications and reinforcements. It cannot travel into Slipspace of its own accord. Apparently, by the time of Halo 2, the Covenant replaced this dropship with the Phantom.