Your pony character has several abilities that come as part of being one of the ponykind.
Ability Score Increase: Your Constitution score increases by 1.
Age: Ponies mature at the same rate as humans, and reach old age at about the same time.
Alignment: Ponies tend towards the lawful alignments, being tied strongly to the forces of destiny from birth. However, there are ponies of every alignment and temperament.
Size: Your size is Medium.
Speed: Your base walking speed is 40 feet.
Four-Legged: Being a four legged creature, you can bear greater weights (50%) than a human of the same Strength without being encumbered. Any roll to avoid becoming prone is made with advantage.
Languages: You can speak, read, and write Common and Sylvan. Sylvan is a musical language of fey creatures, and their sing song can find its way into other languages.
Fingerless: Ponykind may use their mouth as one hand and are considered small sized for sake of what they can wield or not.
Unique Destiny: You gain advantage on checks with a single skill that is tied to the brand of destiny on your flank.
Sub Races: There are many different breeds or tribes of ponykind with wildly different abilities and appearances.