These are droids placed on various maps by the designers of the map. Unlike the Probe Droid, which is player-controlled, and the other droids, which are deployed by players and then follows them around, these droids are stationary.
The Gonk, essentially a box on two legs in appearance, is charged with replenishing the ammunition of nearby infantry and vehicles.
The Medical Droid heals wounded soldiers near it.
The WED Droid takes care of repairs of nearby vehicles. Currently, players can find it in the Alliance hangar on Ryloth.