You can have a wheel alignment done to your car to ensure that the wheels and tyres are in the correct alignment. A wheel alignment sets the correct geometry to give the correct handling and tyre life for your car or truck.
If your steering wheel is off centre or you notice that you car is pulling heavily to one side then you may need a car wheel alignment. Other symptoms are that your tyres are wearing out prematurely or the car is not handling well.
Uneven tyre wear can be due to a few factors: 1) Incorrect tyre inflation 2) Incorrect wheel alignment 3) Worn suspension components - Check you tyre inflation first as this is the easiest and cheapest thing to do (free).
You will need a wheel alignment if you hit a very severe pothole that managed to put your alignment out.
A 4 wheel alignment is when you have all four wheels alignment adjusted rather than a 2 wheel which is just the fronts.