Someone please explain these Specializations?

I am so confused i thought we hard armor mods that you unlock then can use but now im hearing about armor specializations like waterworks and whatnot. What the heck is this…someone help me lol

They’re basically another set of levels (10 or so) that you can go through after you hit the default max rank.

By doing this, you unlock stuff (Armor, skins, and a perk) that you could not unlock by going through the original 50 ranks.