While horses are intelligent animals, they do not understand human speech in the same way that humans understand each other. However, they can learn to associate certain sounds with specific cues or actions through training. For example, a horse may learn that the word "walk" means to start walking, or the word "food" means that a treat is coming.
Horses communicate with each other through a variety of means, including body language, vocalizations, and scent marking. They are able to understand each other's signals and respond accordingly. However, they do not have the same cognitive abilities as humans and are not able to process language in the same way.