Armor
Armor is whatever material your character puts between the dangers of the world and his or her tender skin. Armor comes in several varieties and provides varying levels of protection.
Cloth Armor or Costume Armor is anything typically worn for costuming not otherwise intended as a defensive measure. Cloth Armor takes 10 points of damage before it exposes the user's Body points.
Light Armor is lightweight (at least by comparison) material intended as a defensive measure. Leather and padding are typical examples. Light Armor takes 20 points of damage before it fails.
Medium Armor is typically metal but not thick or intended for full-body protection. Chain, Ringed, and some varieties of Banded are typical examples. Medium Armor takes 30 points of damage before it fails.
Heavy Armor is metal or other hard material intended to take blows for its wearer. Plate is the archetypical example. Heavy Armor takes 40 points of damage before it fails.
Battle Armor is the apex of defensive outfitting. It can be difficult to tell Battle Armor from Heavy Armor at a distance; the difference is in internal reinforcement and such. Battle Armor takes 50 points of damage before it fails.
For game purposes, armor category is determined by appearance. The Texas sun is murderous even in the spring and we prefer not to encourage dangerous steel encasements under the Texas summer sun. The actual material used for construction isn't necessarily relevant. What's relevant is how the overall look reads a few feet away. Cloth armor is awarded for any costuming. There are fabrics available that resemble leather closely enough to present as Light Armor.
Metal armors are a bit more complicated or expensive. Actual metal is an option, but a heavy, potentially dangerous, expensive option. There are lots of good tutorials available on making costume plate from lighter, safer-in-Texas-heat materials. Emily has a great example of EVA foam plate that doesn't use any equipment more exotic than a sewing machine and heat gun (hair dryer works in a pinch.) Chain mail is not especially difficult to 3d print and paint.