When all is not well with the way the teeth “mesh” with each other, there is a “bite problem.”
Sometimes, the existence of the problem is obvious. The solution to the problem is equally obvious. As an extreme example, if the teeth aren’t meshing because of a broken jaw, then surgery is an obvious solution. If the upper and lower jaws grew at different rates, then orthodontics (moving teeth) comes to mind.
But, most of the time, problems with the way the teeth mesh are not obvious. But, such problems exist quite often. So we deliberately look for them. Why would we look for trouble? Because of the damage and suffering a faulty bite can cause.
When analysis of the bite (diagnosis) finds causes other than those mentioned above, then bite adjustment or night guards may be called for. The intent of both of these therapies is to provide an ideal mechanical environment for the teeth.
For that last sentence to make sense, you need read Headaches, TMJ and The Bite.