can u be more specific mano?
I guess in a way its similar to Reach. You gain SR ranks . Each SR ranks give you one SR point which you can use to buy use to equip weapons, greandes, armor abilities, etc to your loadouts, SR ranks also give you some new Armor and Emblem unlocks as you level up. But its not an actual competitive rank like normal because you can gain xp towards your SR rank from campaign and Spartan Ops also. It really doesn't mean anything outside of you put time into the game. 343 studios says the game does actually have an MP rank system but it is invisible to players but they'll be releasing an update something in the next couple months for players to see it. Pretty much most people are going to be using the SR rank as the rank since it pretty much says how much time you've put into the game one way or another. In a way SR is rank but not in a way thats exclusive to MP only.
Armor screen. Some armor you get by ranking up and some comes from completing challenges.
You can see everyones SR ranks throughout the game
Gaining xp at the end of the match screen you can see the SR rank