As you might expect, Juan Garcia is a red wine grape from Spain. Largely used for blending in central Spain, the grape produces a center of the palate wine, typically not made into a varietal which which is heavy on the oak. That center of the palate makes it a good choice to "thicken" softer reds like Grenache, while allowing it to also be used in more international blends. Overall the wine, if you can find it in a varietal specific wine, relates most closel to Merlot grown in the new world.
Local Spanish vintners will argue over where the wine was truly first developed, but it is clear this isn't a grape central to the Spanish wine industry.