You are proficient with light armor.

Benefit: When you wear a type of armor with which you are proficient, you get to add the armor's entire equipment bonus to your Defense.

Normal: A character who wears armor with which she is not proficient takes an armor penalty on checks involving the following skills: Balance, Climb, Escape Artist, Hide, Jump, Move Silently, and Tumble.

Also, a character who wears armor with which she is not proficient adds only a portion of the armor's equipment bonus to her Defense.