It can be confusing to know when to use the four-wheel drive and when not to. It will help if you know what the differences are between the various types of drive systems, particularly Jeep four-wheel drive systems, as there is a lot of confusion regarding: 4WD, 2WD, Part-Time 4WD, Full-Time 4WD, Automatic 4WD, All-Wheel Drive, and what it means to shift on the fly.