Apologetics is, simply put, giving answers and responses to objections that come to or against Christianity. The world "apologetics" means "defense." Scripture enjoins every Christian to be ready to give an answer (1 Peter 3:15). All Christians, therefore, should be "in training" as they read their Bibles so that they might learn how best to respond to those who would oppose the Christian faith.
In our apologetic responses, we should recognize the following: 1. If Christianity is true (which it is), anything opposing it is, by definition, false. 2. Therefore, it is often useful to "stand on the ground" of those who would object to Christianity in order to show that, in fact, there is no ground to stand on after all. 3. It is also useful to ask the objectors to stand on the Christian's ground in order to show and explain how the Christian position alone is able to give an adequate account of the facts around us, including who we are as human beings.
K. Scott Oliphint, Ph.D. is professor of Apologetics and Systematic Theology at Westminster Theological Seminary.
For Professor Oliphint's full treatment of this question:
K. Scott Oliphint, The Battle Belongs to the Lord.
Professor Oliphint's recommended extra resource on this question:
Greg Bahnsen, Van Til's Apologetic: Readings and Analysis