[Scatty]

Those two defense and attack values, displayed on the big blue-black shield and axe in the statistics screen, inscrease only 1. when your Strength and Dexterity values increase (through drinking potions) and 2. when you're wearing one or two (the game doesn't seem to register more than two) Rings of Protection in the inventory, in the Body area. And through the enchant spells, but then only temporarily. Those proficiencies cannot be trained up.
They directly affect your chances of avoiding being hit, to hit an enemy (I think) and certainly the amount of damage done when you hit someone.

There're also two proficiencies which can be viewed in the inventory screen, if you click on Torso armor you're wearing and the weapon you're wielding. Since all armor worn in Torso spot is of the same class, your proficiency with it increases effecitveness in either robes, leather armor, chain or plate armor. It is trained only when you receive a hit from enemy.
Weapons are of different classes, so if you're wielding a Longsword, your profiency with any sword (be it Two-Handed or Short Sword) increases the more you attack with it. If you switch later to a War Hammer, it's a different weapon class so you'd have no proficiency in it and need to train it through attacking enemies. Same with Dagger class and Bow (all bows, crossbows and slings) class weapons.
These two proficiencies lower the chance of you being hit by enemies and your chance to hit them with the weapon you're wielding.

Now, I have no idea how exactly the four different proficiency levels co-operate with each other, but I guess (from observing while playing) that they simply stack with each other. The two defense proficiencies don't seem to reduce the damage received, only lower the chance of being hit.