The answer to this question depends on whether you are a dressage, show jumping, western, or leisure rider. Western riders generally use wheel spurs. They are long and have a rotating wheel at the end. You will also find rowel spurs among dressage riders. Dressage riders often use styles with straight spurs that are bevelled or rounded at the end. If the end of the spike is a ball, they are round end spurs. If the end of the spike has a hammer shape, they are called hammerhead spurs.
Show jumpers can also use these styles, but they use them less often. For leisure riders, all types of spurs are actually unnecessary. When you start riding with spurs, you should first choose the mildest possible versions. These are all models whose spikes have a rounded end.