Yep. Any tire on any wheel almost always needs a certain amount of weight to balance it. Wheels and tires both will have heavy spots in them from the manufacturing process. Even with perfect size, shape, and diameter of the finished product the materials used will have inconsistancies in them. It's much easier to add a weight than try to make a wheel or tire than doesn't have an extra ounce of weight on one side of it.
When a bike wheel/tire is on a balancing stand or a computerized machine it's spun around just as if it were on the bike. As it slows downs eventually the heavy spot will wind up at the bottom. The wheel on a balancing stand will slow almost to a stop then rock back and forth as the weight settles. The heaviest point will obviously be at the bottom from gravity. You then add weight opposite that(12 oclock) and spin it again. If you added the correct amount of weight the wheel will spin for a very long time and eventually just slow to a stop. If you add too much or too little, or in the wrong place, you'll continue to have the same or similiar problems.
If you're riding on unbalanced bike tires there usually isn't a problem or vibration until you reach triple digit speeds. Although it can affect handling and ride quality at normal speeds also, as well as affect tire wear.
Just consider how you think your bike would ride and handle if you put a 10 pound weight on your wheel at any given point around the inside of it. That weight would take effort to be moved to the 12 oclock position of the wheel, then gravity would pull the weight down rapidly and this would repeat.
Every time that heavy spot reaches 6 oclock you'll feel it. The off balance of this will cause a vibration.
10 pounds of course is very exagerated, but the effect is the same, and noticeable even within an ounce or two of weight.
Does that make sense?