Just a matter of terminology here.
RBA = Re-Buildable Atomizer (generic term for any rebuildable)
RDA = Rebuildable Dripping Atomizer (used for direct dripping, for example, a Quasar)
RTA = Rebuildable Tank Atomizer (integrated with some sort of liquid feed tank, for example, a Kayfun)
They all are small devices with screws to capture wire that you build vaporizing coils upon yourself. All atomizers have coils in them, it's just that you can rebuild these yourself using wire and wick. It's fun, it's easy, and it's WAY cheaper than buying ready-made atties.