Jodhpurs in their modern form are tight-fitting trousers

Trousers

Trousers are an item of clothing worn on the lower part of the body from the waist to the ankles, covering both legs separately...

 that reach to the ankle, where they end in a snug cuff, and are worn primarily for horse riding

Equestrianism

Equestrianism more often known as riding, horseback riding or horse riding refers to the skill of riding, driving, or vaulting with horses...

. The term is also used incorrectly as slang for a type of short riding boot

Riding boot

A riding boot is a boot made to be used for horse riding. The classic boot comes high enough up the leg to prevent the leathers of the saddle from pinching the leg of the rider, has a sturdy toe to protect the rider's foot when on the ground, and has a distinct heel to prevent the foot from sliding...

, also called a paddock boot or a jodhpur boot

Jodhpur boot

The jodhpur boot is an ankle boot designed as a riding boot with a rounded toe and a low heel. They originally fastened with a strap and buckle, but today the term also includes designs with straps that do not wrap entirely around the ankle and the elastic-sided design without a strap also known as...

, because they are worn with jodhpurs. Originally, jodhpurs were snug-fitting only from just below the knee to the ankle and were flared at the hip; modern stretch fabrics have allowed jodhpurs to remove the flare and yet remain supportive and flexible.
Jodhpurs originally were long pants, reaching to the ankle, snug from the calf to the ankle, with reinforced fabric protecting the inner calf and knee from rubbing.