1. Lift Kits
We'll start off with lift kits. If you're looking to get the most functionality out of your build, a lift kit is the way to go though they're generally more expensive. Lift kits will allow you to lift your truck up to 3 inches or more and often come with a lot of other suspension components like crossmembers, sway bar links, and drop brackets. These lifts move some mechanical components of your truck higher to allow for better ground clearance. This is often why you'll notice a lot more parts that go into a lift kit when compared to a leveling kit.
2. Leveling Kits
This is where most people start to get confused because a leveling kit does in fact lift your truck. They usually allow up to 3 inches of lift but not any more than that. However the main difference isn't the sizing, it the way the truck gets lifted. From the factory, trucks usually come with the rear end sitting higher than the front, this is known as rake. The thinking behind this is that if you have a truck, chances are that at some point you're going to be hauling something in the bed or pulling something behind you. By giving the truck rake, manufacturers can design the truck to sit level when under load. A leveling kit simply lifts the front of your truck to sit even with the rear for a more uniformed look. Keep in mind that since you made the truck sit evenly without load, when it has load it will probably end up squatting.