The purpose of apologetics, or as it has been traditionally called fundamental theology, is to show the rationality of believing in the Christian religion.
This topic is extremely important, especially in our day when the intellectual foundations of the faith are so commonly challenged.
Apologetics is also important for a second reason.
Theology, in the strict sense, tells us what revelation means. But we can’t know what revelation means without presupposing that revelation exists. So while theology tells us the meaning of revelation, apologetics shows us the existence of revelation.
For this reason, fundamental theology is foundational (go figure) to theology proper.
This video will give you the structure of the Apologetics curriculum as the Aquinas School Of Theology And Philosophy.