Types Jobs of a spartan can have....

I was wondering, do Spartans have a job in the UNSC.
I am a United States Marine, and my job is base firefighter (Crash Crew).
For example… are there Sniper Spartans, Spartans that do black op missions, pilot Spartans, etc.
I was wondering this because in halo reach there are different types of armor
Like Security, commando, haz ops etc. Do Spartans get armor that matches there job, or career
Thank You
Nateisrelycool