Armor in Elders Scrolls Online protects players from Physical Damage sources and provides the player with Spell Resistance on a 1 to 1 ratio. This means that for every point of Armor you have you will also have 1 Spell Resistance. Players can select from Light, Medium and Heavy armors. Each one has benefits and drawbacks. Players are free to mix and match pieces at their leisure and can customize the Style of Armor to reflect their choice of appearance (there are several to choose from for each type).
One acquires rank in an Armor Skill line by simply wearing a piece of that type and gaining experience from any source. This is different than how previous games in the Elder Scrolls series worked, whereby, a player must actually be hit while wearing that armor type to increase experience in that line. Players can wear one of each type and simultaneously rank up all three types if they are so inclined. Equipping more than one piece of armor of a specific type does increase the speed in which you rank up that Armor Skill line.
Armor Sets can be crafted, dropped from enemies, found in chests across Tamriel and in PvP reward bags and vendors in Cyrodiil. A Blacksmithing Station is required and adequate training in Blacksmithing is necessary to create Heavy Armor, while a Clothier Station and adequate training in Clothier is required to make Medium and Light Armor. Highly skilled artisans can also upgrade Armor dropped from enemies.
Different Armor pieces can have different Traits and Glyphs attached to them when dropped by enemies or via crafting. They can also be crafted with set bonuses at unique Crafting Stations across Tamriel. For a full list of these and the locations of these Crafting Stations please see the Blacksmithing or Clothier pages.
Each Armor skill line has its own tree. These are Light Armor Skills, Medium Armor Skills and Heavy Armor Skills. Each tree has 1 active skill and 5 passive skills to choose from. It is not required to put points in any of them to use armor of any type. All classes can use all types of armor by default.