You summon a spirit that assumes the form of a loyal, majestic mount. Appearing in an unoccupied space within range, the spirit takes on a form you choose: a griffon, a pegasus, a peryton , a dire wolf, a rhinoceros, or a saber-toothed tiger. The creature has the statistics provided in the Monster Manual for the chosen form, though it is a celestial, a fey, or a fiend (your choice) instead of its normal creature type. Additionally, if it has an Intelligence score of 5 or lower, its Intelligence becomes 6, and it gains the ability to understand one language of your choice that you speak.
Your steed servers you as a mount, both in combat and out, and you have an instinctive bond with it that allows you to fight as a seamless unit. While mounted on your steed, you can make any spell you cast that targets only you also target your steed.
(see page 156 of Xanathar's Guide to Everything)