The difference between Anterior and Posterior

When used as adjectives, anterior means before in place, whereas posterior means located behind, or towards the rear of an object.

Posterior is also noun with the meaning: the buttocks.

check bellow for the other definitions of Anterior and Posterior

Anterior as an adjective:

Before in place.
Anterior as an adjective:

Before or earlier in time; prior to; preceding.
Anterior as an adjective (anatomy):

Nearer the forward end; nearer the head of an animal or the front of a human.

Posterior as an adjective:

Located behind, or towards the rear of an object.

Examples:

"synonyms: back hinder rear"
Posterior as an adjective:

Following in order or in time.

Examples:

"synonyms: later"
Posterior as an adjective (anatomy):

Nearer the back end; nearer the caudal end of the body in quadrupeds or the dorsal end in bipeds.
Posterior as an adjective (botany):

Next to, or facing the main stem or axis.