You have studied the use of armor, and have improved your ability to use armor effectively.
Options:
While you are wielding a shield or tower shield, or wearing Medium armor or Heavy armor you are proficient in, Bludgeoning, Piercing, and Slashing damage that you take is reduced by your Proficiency Bonus.
While wearing Light armor or Medium armor that does not impose Disadvantage on your Stealth checks, Opportunity Attacks are made against you with Disadvantage.
When you wear Medium armor you are proficient in, you can add 3, rather than 2, to your AC if you have a Dexterity of 16 or higher.
Wearing Medium or Heavy armor which you are proficient in does not impose Disadvantage on your Stealth checks.
You may ignore the minimum Strength requirement of Heavy armor you are proficient in.
While you are wearing Heavy Armor you can use your Strength modifier in place of your Dexterity modifier for your Initiative rolls. If your Dexterity modifier is negative than you must include the negative amount to your Initiative.
You gain proficiency in Heavy armor (you must be proficient in Medium armor from a source other than this feat to choose this bullet).
While wearing Light armor, you may add your armor's AC bonus to your Dexterity saving throws. For example, if you are wearing Leather Armor you can add 1 to your Dexterity saving throws.
While wearing Light armor which you are proficient in, and you are damaged by a melee attack, you can take a Reaction to move 5 feet in any direction without provoking an Opportunity Attack.
You gain proficiency in Light armor.
You may wear a Hauberk armor, Hide armor, or Mail Shirt as Light armor for the sake of determining proficiency. When wearing a Hauberk armor, Hide armor, or Mail Shirt, you can add 3, rather than 2, to your AC if you have a Dexterity of 16 or higher.
When you wear Medium armor you are proficient in, you can use your Constitution rather than your Dexterity for the additional armor normally provided by Dexterity.
You gain proficiency in Medium armor (you must be proficient in Light armor through a source other than this feat to choose this bullet).
You gain proficiency with Shields (includes bucklers, shields, and tower shields).
While you are wielding a shield or tower shield, or wearing Medium armor or Heavy armor you are proficient in, Bludgeoning, Piercing, and Slashing damage that you take is reduced by your Proficiency Bonus.
While wearing Light armor or Medium armor that does not impose Disadvantage on your Stealth checks, Opportunity Attacks are made against you with Disadvantage.
When you wear Medium armor you are proficient in, you can add 3, rather than 2, to your AC if you have a Dexterity of 16 or higher.
Wearing Medium or Heavy armor which you are proficient in does not impose Disadvantage on your Stealth checks.
You may ignore the minimum Strength requirement of Heavy armor you are proficient in.
While you are wearing Heavy Armor you can use your Strength modifier in place of your Dexterity modifier for your Initiative rolls. If your Dexterity modifier is negative than you must include the negative amount to your Initiative.
You gain proficiency in Heavy armor (you must be proficient in Medium armor from a source other than this feat to choose this bullet).
While wearing Light armor, you may add your armor's AC bonus to your Dexterity saving throws. For example, if you are wearing Leather Armor you can add 1 to your Dexterity saving throws.
While wearing Light armor which you are proficient in, and you are damaged by a melee attack, you can take a Reaction to move 5 feet in any direction without provoking an Opportunity Attack.
You gain proficiency in Light armor.
You may wear a Hauberk armor, Hide armor, or Mail Shirt as Light armor for the sake of determining proficiency. When wearing a Hauberk armor, Hide armor, or Mail Shirt, you can add 3, rather than 2, to your AC if you have a Dexterity of 16 or higher.
When you wear Medium armor you are proficient in, you can use your Constitution rather than your Dexterity for the additional armor normally provided by Dexterity.
You gain proficiency in Medium armor (you must be proficient in Light armor through a source other than this feat to choose this bullet).
You gain proficiency with Shields (includes bucklers, shields, and tower shields).