How to tell you need one
The steering wheel is not straight when the car is going straight. The car drifts toward one side on a level road. The inside or outside edge of a front tyre is visibly more worn than the rest of the tread. Any of those three is worth checking.
Alignment is not the same as balancing
Alignment sets the angles the wheels sit at. Balancing corrects weight distribution within a wheel and tyre. Alignment fixes pulling and uneven wear; balancing fixes vibration at speed. They are different jobs and they solve different symptoms.
Some vehicles need more than an alignment
If your car has forward-facing cameras or radar for lane keeping or adaptive cruise, changing the alignment can require those systems to be recalibrated afterwards. We will tell you if yours is one of them.