Well those are post ranks.
Turret is the lowest, then it's speeder [100 posts]
gaurd [1,000 posts]
mortar [3,000 posts I THINK]
disruptor[ 5,000 posts.]
Heavy cruiser [10,000 posts]
So on.
As for things like "soldier" and "LT"
Soldier is a higher rank than private, which you get for maturity.
You can vote for things, and see more threads.
LT is more important. And can send awards, and many more.
General basically controls the forums, apart from geoff, and war veterans are retired generals.