What do you do with a carrot on a stick on minecraft?

When you put a saddle on a pig you can control and ride the pig and use the carrot on a stick to control the direction that the pig moves, I believe that it also gives them a little speed boost when you right click it when you are riding them.

If you put a horse saddle on a pig you can ride a pig like a horse. Unfortunately you can't control the pig in any way, it goes where it wants to.

That's where the carrot on the stick comes in. If you are riding a pig and break out the COS the pig will follow the carrot.