Hi Lanee, Generally photo labs will either crop or fit your images. In both these cases your pic will not be distorted and will be proportioned just like the original.
If your photo lab crops your image it will have the top and bottom or left and right cropped (depending on the size of the print vs the size of the photo).
If the photo lab allows you to fit your images, then the pic will have black or white bands along the top and bottom or left and right.
Generally photo labs also give you a preview of how your photo will print from within your shopping cart and may allow you to position the image when cropping.
If you are talking about printing at home, the same rules apply and the outcome will depend on your printing settings.