"true"-ing something simply means to make it...perfect...if you will. Have you ever heard of "truing a comm?" Its the same idea. You cut your motor, you cut foam tires....the same principles apply to both things.
You only need one if you run foam tires on a touring or 12th scale car....gas or electric. On Road only....there's no use for these in off road! If you want maximum preformance out of your on-roader, then yes, you should definetely get one!....If you do get one, check out the "HUDY" lathes, best in the business!
TQ Racing Wire