Here is a comprehensive summary of the article:

The wild horse (Equus ferus) is a species that includes the modern domesticated horse (Equus ferus caballus) and the endangered Przewalski's horse (Equus ferus przewalskii), which was once extinct in the wild but has been successfully reintroduced in parts of Mongolia, China, and Kazakhstan. The European wild horse, or tarpan, went extinct in the late 19th century, though modern studies debate whether it was truly wild or a feral hybrid. Since then, attempts to "recreate" the tarpan have produced breeds like the Heck horse, though these are genetically based on domestic stock. Importantly, the term "wild horse" often refers colloquially to feral horses—such as the American mustang and Australian brumby—which are untamed descendants of domesticated horses, not true wild subspecies. Historically, wild horses ranged across the Old World during the Late Pleistocene, adapting to environments from temperate forests to tundra, with body masses varying from about 250 kg in living Przewalski's horses to over 600 kg in some extinct Pleistocene populations. These horses live in hierarchical herds led by a dominant stallion, and while primarily grazers, they may browse on shrubs during harsh winters.