One of the byproducts of lowering a vehicle can be an increase in the amount of negative camber. When looking at the wheel and tire assembly, this can be identified when the top side of the wheel/tire slants inward towards the vehicle's center.
Negative camber is a positive trait for those looking to track their cars or drive spiritedly. It helps the car turn in and the tire's contact patch to remain flat when one side of the car is loaded entering a corner. Also, it's not uncommon for some race applications to see as much as five degrees of negative camber.
Not everyone is looking for large amounts of negative camber for race use. Typically, most passenger vehicles tend not to exceed 1-1.5 degrees as they leave the factory. Having a lesser degree of camber helps with tire wear and is the primary cause for camber correction. Cars with large amounts of negative camber will tend to wear the inside shoulder of the tire more rapidly than the outboard.
If you have lowered your car on a conservative or moderate spring such as an Eibach Pro-Kit Spring Set or H&R Sport Spring Set, your camber specs may still be acceptable according to factory spec ranges without any other modification. However, as you begin to look at more aggressive set-ups, such as coilover kits, you may want to consider camber correction if you're interested in the best possible tire life on the street.
Camber correction can be done using camber correction bolts, adjustable control arms or adjustable camber plates. While all of these methods work great, which type you'll need is dependent on your vehicle type.
For more information on camber, read our tech article on alignment.