Tank style locomotion is where there are no steerable wheels. Rather, wheels on one side of a vehicle move forward, while the wheels on the other side either stay stationary, or reverse (as illustrated in the following diagram). This is also called skid-steering:
This kind of locomotion is great because vehicles can literally turn on a dime (in place). However, the drawback is that it can be jerky when turning while going forward. But as there's no sensitive equipment (just golf clubs), we don't really care if there's jostling of the clubs during turns. All we really want is to make this as inexpensive and simple as possible. You may notice that the front wheel is fixed (doesn't pivot as a caster would). This is of no concern to us as when steering occurs, the front wheel doesn't have a lot of weight on it (the center of gravity is right on top of the main wheels' axle). Therefore, the friction is minimal. If it turns out to be a problem, we can always replace the front...