Armor in Sindome is considered any article of that gives your character any kind of protection. So even an EcoGear softshell jacket is considered armor due to its protection against the elements.
All armor has a set thickness that increases according to the amount it protects the user. So while you can wear several layers of warm clothing you won't be able to wear more than two or three layers of heavy armor.
Up to a level of protection armor is considered an armored clothing production line, like DuWear and neXus. These have several different items of the same line but aren't supposed to make a set where you wear one of each, they are armor with style over substance.
The higher level or armors are sets that are worn over a jumpsuit/bodysuit. This combination of flexible undergarment and harder pieces worn over them is what make the full protection of the set.
Different jumpsuits give different protection and can even fill a gap where the hard shells don't give any protection. One can mix and match different jumpsuits and even armor pieces from different factories/corporations. An example of these is the WJF Judge armor set and Xo3.
==Damage== All armor will work on every attack (some better and some worse) depending on their defensive characteristics. Only when the armor absorbs almost all the damage dealt to your character that a different message will be displayed in combat.
There are no invulnerability spheres in Sindome, so every attack will hurt your character even a little bit.