If you want to know what each stat does for you, go to the character window and hover over a stat (mouse) or select it (controller) and you should get a little tooltip window explaining its effects.
As for tanks, either full VIT or a split between VIT and STR are popular answers. Some tanks go full STR, but that's more popular for Warriors than Paladins. But basically you can't go too far wrong if you're sticking with those two.
(For my own Paladin alt, I'm sticking with full VIT for now while leveling him. Once I get him to endgame and have lots of GC seals, I may get a couple of those point reset items and try out alternatives, but I'm not going to worry about that until later.)