Just because they're small doesn't mean they're babies.
Nothing drives an equestrian crazy faster than someone pointing to a pony and saying, "Awww, what a cute baby horse!"
While it may come as a surprise to many non-equestrians, ponies are not baby horses; they are fully grown equines who mature at a smaller height than their horse relatives.
There are distinct differences
Horses and ponies have a number of physical differences in addition to the obvious difference in height. Ponies are not only shorter, but often wider, with thicker legs and bones and a wider barrel. They are known for being shaggy, and often have thicker manes, tails, and even coats.
While various organizations recognize different heights, the most commonly recognized height for a pony is 14.2 hands and under, or the equivalent of 58 inches, 147 centimeters, measured from the withers. They are remarkably strong for their small size, and larger ponies can even be ridden by adults.
Ponies are thought to have evolved from horses making their homes on the margins of livable habitat, become smaller and hardier to survive.
The confusion between ponies and baby horses is understandable, since the word "pony" is derived from the old French word "poulenet," meaning foal, or baby horse. But if you want to impress a horse person (or at least avoid the eye rolling), point to a pony and say, "Awww, what a cute pony!"
You will immediately gain a few points in their eyes.
According to thesprucepets.com,
"Pony foals are tiny and will mature to the approximate size of their parents. Horses are slower growing, some not attaining full mature size until they are six or seven years of age."
Some first-time horse owners may confuse an adult pony with a young horse. While newborn foals that will grow up to be horse-sized may be no taller than some ponies in their first months of life, their body proportions are very different. Healthy foals, whether they grow up to be horse or pony-sized, can be distinguished from adult horses by their extremely long legs and slim bodies.
While ponies exhibit some neoteny with the wide foreheads and small size, their body proportions are similar to that of an adult horse.
Ponies are known to be very intelligent!
If you're interested in breeds, the Welsh Pony and Cob is a group of four closely-related horse breeds including both pony and cob types, which originated in Wales in the United Kingdom. The Shetland pony is a breed of pony originating in the Shetland Isles, Scotland.
There are actually very few similarities! The only one worth mentioning is that they come from the same family tree. And they both have average lifespans of 25-30 years.
You can overfeed a pony which causes laminitis and founder. So even feeding a pony is different than feeding a horse!
Farmers observed that a pony could outperform a draft horse on small farms. By the 20th century, many pony breeds had Arabian and other blood added to make a more refined pony suitable for riding. But don't mistake a pony for an Arabian horse! They are not considered race horses!