Most tractors have large back wheels so they can be driving over rough ground and for grip when pulling heavy objects. Many tractors have four wheel drive to get extra grip on the hills and in wet conditions. A lot of tractors come with cabins so the farmer can work in wet or on cold days. Most tractors come with a P.T.O. shaft so that when it turns it operates balers. Also tractors can come with linkage to lift round bales.
Tractors also can come with a hydraulic system which makes oil pressure to lift ploughs up.
If you have linkage most tractors which do have weights to stop it from flipping up. Some tractors can have duel wheels which gives twice the amount of grip and reduces the risk of the tractor rolling. Some tractors have power steering to make the tractor easier to drive for the farmer. When you turn the key the engine starts by using power from the battery which goes to the starter motor, which then turns the engine over which pumps the fuel into the motor and starts it. To make it drive you push the clutch and put it into gear and slowly let the clutch out.