Mammals 'eyes generally grow on the front of their heads, which makes it easy to observe the situation ahead and help avoid enemies or capture food. So when an animal attacks another animal, it often approaches slowly from the side or behind.
Of course, even if the eyes are on the front of the head, there are differences in the specific position. The eyes of carnivore are directly in front of the face to facilitate observation of the prey in front, and the intersection of the two eyes can lock in the distance of the target. The eyes of herbivores are long on both sides of the flattened head, which is to facilitate large-scale observation of enemies coming from all directions. Hippo's eyes, nose and ears are all grown on the top of the head, making diving much easier.
Therefore, the eyes are mainly used for observation, but of course, observation does not all rely on the eyes. Mammals living in underground caves often have small eyes or even invisible at all due to the dim light or lack of light in the environment. However, these animals can make up for it by hearing, smell, and touch. Although many nocturnal pterods (insectivorous bats) have eyes, they rely on ultrasound to locate and detect prey or obstacles.