Wheel balancing is a process where the weight of the wheel and tyre are balanced so that the rotation is smooth.
If you are driving and notice that the steering wheel vibrates when reaching certain speeds (ususally above 50mph) this could be an indication that your front wheels on your vehcile require balancing.
You might also notice seat or floor vibrations which could signify that the rear wheels require balancing.
When left for long periods of time incorreclty balanced wheels can lead to expensive repairs such as tyre replacement due to uneven wear and repairs to to steering componements or suspension.
As a rule of thumb it is recommended that wheel balancing is checked as part of the annual vehicle service.