An RCCB is (in practical terms) another name for an RCD. So is ELCB. These days they are all current operated.
You know what an MCB is?
Well, an RCBO is a single device which combines the functions of an MCB (overcurrent and short-circuit protection) and an RCD (Earth leakage protection).
The better makers offer a range of them, so you can have a B32 30mA RCBO for example for your socket circuits, or a B40 30mA for your shower. As far as I know, MEM make the widest range possible, because of the way they are assembled. You can order a D6 100mA, if you want.
They can generally be fitted into a Consumer Unit in place of an MCB. Some are the same width, others are wider and may take up two spaces. this depends on the brand and model.
In domestic consumer units, they will generally cut one pole only (the Phase conductor) although two-pole RCBOs are available to cut Phase and Neutral.
They tend to be quite expensive. However in the respect that, in the event of an earth leakage, they will cut power only to the affected circuit without inconveniencing users on other circuits, they are superior to a split-load arrangement or an installation protected by a single RCD, because either of these will cut power to the other circuits. Quite apart from the inconvenience, this makes them valuable in commercial and industrial environments, because it prevents you losing production on those other circuits. This can save you a lot of money.
I think they're great