The warning system is a way for moderators to keep track of which users are causing offence, or breaking forum rules.
If you are found to be breaking forum rules you may be given a verbal, or official warning. An official warning adds 10% or one block to your warning level. A verbal warning doesnt add anything to your warn level, but does keep a log of why it was given.
Everyone has a warn bar under their topic profile, however only yourself and a moderator can see it, nobody else can. Which is why you will see a warning bar under your name, but nobody elses.
Everyone starts at 0%. And if you follow the rules that will not increase.
If you have any firther questions please feel free to contact myself, or any other moderator.