First off they have a normal lvl system, you level up, put in attribute points (strength, intelligence, agility etc) and then you get some points to put in skills (ironflesh, powerstrike, wound management, trade, block etc) then lastly you get to spend some points in proficiencies (one handed weapon, two handed weapon, bow, throwing etc).
And leveling after a while got reaaaally hard.. i mean extremely hard at a point >,< BUT that only affects skills and attributes, proficiencies on the other hand can always be upgraded by just using a weapon, like if you use a one handed sword much you will get more points with it automatically.
also, you get 1 skill point for every attribute point you pick, you get 2 attribute points/lvl i think, but you get 2 skill points if you choose intelligence... or was it charisma. All attributes affects you differently, like more dmg/hp/ and if I remember correctly the skill points are bound to the attribute, so if you want to have lvl 4 riding you need lvl12 agility (1/3 of the attribute).
Thats like.. about it i think