Armor changes your appearance, protects you from hits, and can occasionally be used to disguise yourself. Having the best armor available is far more important than having the best weapon available, regardless, you probably will never need to buy armor. If you diligently loot corpses you will have all the armor you need, plus plenty of extra suits to sell. The only time you may need to buy armor is a set of combat armor in the hub, but even this is unnecessary.
ARMOR CLASS (AC): The higher the armor class the lower the chance you will be hit. Some heavier types of armor may decrease your armor class while still being an improvement over the old armor.
Normal damage covers bullets, shells, cutting instruments, blunt force, and HTH attacks.
In regards to armor stats damage threshold is always expressed first and damage resistance second. Normal: 4/30 would mean a damage threshold of 4 and a damage resistance of 30% against normal attacks.
DAMAGE THRESHOLD: DT is subtracted from the hit point damage of the attack. For example, if you are shot and hit by a raider, his attack might do 50 damage. Let's assume you have a DT of 5, so the first five points of damage stopped, with only 45 left.
DAMAGE RESISTANCE: After the DT subtracts its amount from the damage received your damage resistance comes into effect. DR is expressed as a percentage. This is the percent of the remaining damage that is nullified. For example, in the above attack you took 50 points of damage, after your DT stopped 5 you were still left with 45 damage. Lets assume you have a DR of 20%. 20% of 45 is 9. Subtract 9 from the 45 and you take 36 damage from the original 50.
Leather Jacket: Wear this near the dog in Junktown and it will join you. Wear this in the raider's camp if you are a male and they may think you are a ghost. (Easter Egg: This is the one-armed leather jacket from Mad Max).
Leather Armor: Good for the beginning of the game.
Combat Armor: If you save up you can buy this in the hub. I only suggest this if you can get a lot of money early on, otherwise you can find a pair in the Glow.
Brotherhood Armor: It's a modified combat armor, you get a suit for free when you join the Brotherhood, talk to Talus to get clearance to check one out.
Tesla Armor: Incredible resistance to laser and plasma weapons, this can be very useful near the end of the game when the enemies prefer energy weapons.
Power Armor: This is the armor the Brotherhood paladins wear. It increases your strength by three, provides incredible protection, and makes you look really cool. It can only be acquired in the Brotherhood bunker.
Hardened Power Armor: After you fix the farms in Adytum Smitty will upgrade your power armor for free! This is the best armor in the game. Better in every way than ordinary power armor. Still gives +3 strength.
Robes: These are the purple robes that the Children of the Cathedral wear. They provide pathetic protection, but if you wear them and leave your NPC's behind you can sneak into the military base and cathedral without being attacked.