Hub centric means that the center mounting hole of the rim fits tightly around the hub of the truck. Lug centric means that the rim, since its an aftermarket rim is not made specifically for the Titan's axle but has the same lug pattern but you should use a hub ring so that the center hole of the rim fits tightly around the hub of the axle. See:
http://www.miata.net/garage/hubcentric.html
I am very interested in the rims but I'm hoping that they are hub centric as these fit better without having to use hub rings.
Thanks,
John