Directional terminologies are used in order to describe the position of structures in the body according to the position of other structures. When we talk about bipedals, It's important to mention that we have a vertical reference of those organisms positions. For bipedals, some examples of directional terminologies are:
Anterior, posterior, distal, proximal, dorsal, ventral, superior, inferior, etc.
On the other hand, when we observe quadrupedal animals, the reference is horizontal, and that's how some terminologies change. For those organisms, we have terminologies such as:
Ventral, which corresponds to anterior.
Dorsal, which correspons to posterior.
Other terminologies, however, remain the same, such as medial and proximal.