Question about Evasion rating

Hello im a new in POE and i don't really understand what evasion rating is so i only wear stuff with armour so my question is what is the difference between evasion rating and armour and which one would be better to wear for shadow.

Evasion Rating gives you a chance to evade attacks ( not spells ). When you evade an attack, it deals no damage.

Armor Rating reduces the damage from physical damage. The higher the damage taken, the less armor will reduce it.

In short, armor is for smoothing out damage spikes for medium hits, and making lots of small hits ( like a group of white archers ) negligible. Evasion will result in spikey damage taken, but can completely ignore some hits.

As a shadow, you'll have more access to int and dex passives, which means you'll probably be able to wear better evasion gear than armor early on. There is a keystone passive called Iron Reflexes ( bottom right of tree ) that can convert all evasion rating to armor. This is a really good passive, as each point in dex will add a % modifier to evasion. There is no armor analogue based on stat points.

Because of the way armor works, having a little bit of armor is kind of a waste. I'd go all armor or no armor and use Granite Flasks ( add 4000 armor ) when you need physical damage reduction.

Also note evasion is normalized to prevent long streaks of hits and misses.

you can find more details in these links if you feel like reading :P

http://en.pathofexilewiki.com/wiki/Evasion

http://www.pathofexile.com/forum/view-thread/11707

Amour and Evasion each have their own strengths and weaknesses. As was mentioned earlier, armour is good against many small hits, while evasion is good against slower but harder hits (such as bosses/rare mobs). For example, an armour character would have no trouble wading into a crowd of mobs, but will find it difficult to face-tank Brutus. An evasion character will have to constantly stay mobile with skills like Whirling Blades when fighting mob packs, but will have no trouble face-tanking Brutus.

The two stats also have different dynamics when you are stacking them. Armour has increasing marginal returns, meaning that each point of additional armour you get gives you more benefit per point. Evasion on the other hand has decreasing marginal returns, so you can get quite a lot of benefit by stacking a moderate amount of it, but to really max it out requires a significantly higher investment.

These different dynamics mean that with armour, you need to stack it pretty much exclusively, whereas for evasion, it is most efficient to grab the "low-hanging fruit" and use the remainder of your budget to stack another defensive stat. Thus, evasion is much more easily used in a hybrid build than armour. In fact, even "pure-evasion" builds are really a hybrid of evasion+dodge, which is obtained from the Acrobatics nodes.