Hey, welcome to the forum.
For starters, there are two kinds of wheels available on buses, so we need to find out which kind you have. Since you don't mention anything "weird", I'm guessing you have a small circle of normal studs and nuts, like a passenger car or pickup-truck, just larger. (The other kind has nuts out near the rim.)
Do the studs have a square tip? Then you have double nuts. That means that the square tip is actually on an inner nut, which has threads both inside and outside. The inner nut holds the inner wheel, and then the outer wheel is held onto the inner nut by the outer nut.
The normal procedure is to unscrew the outer nut off the inner nut, the latter remaining tight. But once in a long while the nuts are not correctly tight, and the inner nut rotates when you turn the outer. So put your wrench on the nut and watch if the square tip also rotates. If it does, you need to hold the square tip.
Let's see if that gets you any further.
Oh... and there are no stupid questions.