Reserve dining is a section of the MDR on all ships except Sun where it is an actual separate restaurant. It'll be listed in the daily event planner as to where the Reserve dining section will be .
The Reserve section has different linens, flowers, menu covers, but same menu, with an additional item or two each night, ie lobster thermidor or lamb chops or a special pasta or such..
Ni reservations needed at all, walkup when ready and tables will be available - usually. Maybe a short 5 minute wait.
If you want the same area/table or wait staff every night, just let the maitre'd know.
Happy sails.