A regroovabletire is just that - you can have new thread grooves cut into the tire body after the originals have worn away. A typical big tire will have a tread depth of 15/32"-22/32" and the new grooves can generally be cut nearly as deep. That effectively doubles the mileage you can get on the tire. But since RV tires seldom travel many miles per year, they generally die of old age or road hazard by the time the first set of grooves wear out anyway. So regrooving is meaningless to 99.9% of RVers. For long hual truckers, though, it can mean they get a lot more tire mileage for their money.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL