What's a specialization?

What is a specialization? Under the career tab in the game is a list of specializations. Apparently, everyone starts out as “Spartan-IV,” according to the game, but then there are others like “Wetwork,” “Engineer,” “Operator,” “Pioneer,” and a couple others. It also says something about neeeding to complete the active specialization in order to advance. What are these specializations? What do they do for you? Like, what do these mean?

you start unlocking them at SR50. They provide alternate armor, weapon skins and tactical packages

Think of it kinda like a prestige. (Sorry for using a COD term, but it’s the best example I can come up with.) Once you get to SR-50, you can choose a Specialization, and then you basically repeat the last 10 levels. You get new armor, visor color, or a weapon skin every rank, and once you get to the last level of it, you get a Support Upgrade or Tactical Package to use. Then you pick another one and do the same thing again until you get to SR-130.