What do you call the pony that walks the racehorse?

Answer 1

Walk -> Trot -> canter -> Gallop

This is the 4 stages of a horses performance.

Answer2:

When a pony is running at full speed it is called a gallop, just like with a full sized horse.

Answer 2

Ponies that walk alongside the racehorse are called the lead-horse. They are often used to keep a balance between the cart or vehicle that they are moving.