Emerald Armor is simply an emerald form of armor. It contains boots, leggings, a helmet and a chestplate.
Photo credit to Chupacabra boy
The Defense points of emerald armor are less than diamond but more than iron/chain.
A full set will equal 17 defense points with a helmet being 3; A chestplate being 7; Leggings being 5 and boots being 2.