Briga is a pumpkin like herb that you can collect from the MuMu Farmlands in Altgard. This is the only place in the game you are able to gather Briga which requires an Extract Vitality Skill of 10. Briga is used in the Cooking Profession to create a subpar dish that raises your MP. Not many people are interested in this dish, so if you're looking to farm Briga and sell the Fruit/dish, don't bother. =P
The only reason I really recommend gathering Briga is to raise your Extract Vitality Skill. Actually if you're looking for an overall good place for you to raise your Extract Vitality the MuMu Farmlands is actually a halfway decent place.