Before you go out and blow up your first trogg, wolf or boar you’ll need a basic understanding of what your various stats are and how they will affect you. Leveling up only raises your stats a little bit so you’ll need to increase them with equipment. It would be nice if you can raise them all evenly, but equipment doesn’t do that and individual pieces have two or three stats at best. So it is best to try to pick the stats that fit your play style (Fire, Frost, Crit, Slow ect) and load up on those. Stats can be broken into three groups. Stats, Attributes and Modifiers.
But before you learn about stats you need to learn about the battle engine in Warcraft. It is broken into two intermixed groups, percentage and damage. The percentage system is always consulted first because it determine chance to hit, dodge, parry resist and crit chance. Once those factors have been established the damage system takes over and determines how much damage is dealt. Think of it like a real life fighter. First they swing and may make contact or miss. If they make contact then the amount of strength they have determines how badly their opponent is injured.
Since computers have limited intelligence the only way they can adequately replicate “skill” and still have a semblance of randomness is with percents. For this example let’s look at your chance to hit a target. Against an enemy with an equal level you have a 95% chance to hit. When you swing your weapon the game picks a number between one and one hundred by rolling a one hundred sided dice and if it is less then ninety five you will connect. According to the law of percents this means that if you swing your weapon one hundred times ninety five of them will hit and five will miss. Now let’s look at your chance to get a critical strike with a critical strike percentage of 25%. If you have won a chance to actually hit, the computer rolls another one hundred sided dice and this time if the number is twenty five or less you will land a critical strike. This time the law of percents says that out of one hundred hits you will land twenty five critical strikes.

The percentage system with magic is much simpler than the percentage system with melee. There are no parries, blocks or dodges with magic, instead you have to deal with

resists. A mage can't miss like a melee character, so instead their spells have a chance of being resisted. Resists can also come from magical resistance, but that comes later on. The chance that you will hit with a spell is based off of the difference between your level and your opponents. If you are both equal you have a 96% chance of hitting with a spell and 4% chance of having one of your spells resisted. If you are three levels higher than your opponent you will have a 99% chance of hitting with your spells. But if you are three levels below your opponent you will have an 83% chance of hitting. Just as melee characters need to gain melee hit gear, you will need to improve this with spell hit gear.
After the percentage system has run its course its time to determine how much damage is dealt. This system has two stages, attacker damage dealt and enemy damage mitigated. Damage dealt can also be divided into two steps, white damage and green damage. White damage is your base damage from your weapon or base damage from your spells. It gets this name because the base damage of weapons and spells is printed in white text. Weapons and spells have a minimum and maximum amount of damage they will do on an attack. Every swing or cast will pick a number between the two and that will be your base damage. The choice is completely random and can’t be influenced in any way, and in order to make it more understandable their average is displayed as damage per second or DPS. Green damage gets its name from the fact that all modifier stats have green text. This is your final damage because it takes your white damage and adds on the effect of stats like strength, attack power or spell damage. In general it is what you will focus on the most when determining your damage output. Once you have unleashed your damage you are effectively done and now the focus shifts to your opponent. First the game determines whether or not the enemy will dodge or resist the damage. If they do then your attack has been neutralized and the process starts over again. If it connects with the enemy it then takes your green damage and subtracts some based on the enemy’s damage mitigation.

The only way an enemy can mitigate your spells is through resistances. They work somewhat like armor, but don't reduce a set amount and have a chance of neutralizing any damage dealt. Magical resists can come in two forms. A full resist, or a partial resist. When a full resist occurs your target will receive no damage at all. This is important because some spells, mostly in the frost tree,

are known as binary spells. They will either cause full damage, or be fully resisted. If a target partially resists a spell they will only take a small portion of the damage you would have dealt. The actual amount is dependent on how much of a resistance they have to that school of magic. If they have a high amount of resistance, they may only take twenty five percent of your damage, if they have low resists though they might take seventy five percent of your damage. The amount they ultimately take is determined by their magical resistance. Just as adding spell hit helps reduce spell “misses” spell penetration can help reduce resists. Spell penetration items reduce your targets magical resistances by a set amount, but they are mostly only needed in PVE groups and raids.
Now that you understand the battle system it’s time to learn about stats, attributes and modifiers. The five basic stats are simple because their main function is to increase your attributes or modifiers. Strength, Agility, Stamina, Intelligence and Spirit each have a specific role and certain builds will have you load up on one more than the other. Since the primary purpose of stats is to increase the effectiveness of your attributes their explanations are rather straightforward.
Attributes are things like Defense, Armor and Attack Power. They are all dependent on your stats and are a bridge between stats and the battle engine. Each of these are increased by your stats but they can also be increased directly by items.
Modifiers deal directly with the percentage system and determine your chance of hitting, dodging and landing a critical strike. Most of their values come directly from your stats, but there are also pieces of equipment in game that will increase them as well. In the 2.0.1 patch this was changed from a straight percentage system to a rating system where a certain number of rating would equal an extra one percent. As you increase in level your rating requirement will rise as well so you don’t hang onto items below your level.