what are couplings?

no, couplings are a piece of leather that clip on each side of the bit under the chin with a centre ring to clip the leadrope to.

roundings are used with pelhams and are attached to the same side, top and bottom ring of the pelham.
 
No.
Roundings are designed to be used with a pelham bit (fastened to top and bottom rings so you only have to use one rein.
Couplings are used for an in hand bridle (go behind the mouth from each side of the bit, so again you have one central rein attached to give you an even contact.
Couplings can also be two very short leads, joined by a ring so that you can lead two hounds/dogs together from one lead.
Hope that makes sense!
 
Top