What is apologetics? I will let one of the most prominent apologists of our day—William Lane Craig—answer that question.
“Apologetics (from the Greek apologia: a defense) is that branch of Christian theology which seeks to provide rational justification for the truth claims of the Christian faith. Apologetics is thus primarily a theoretical discipline, though it has a practical application. In addition to serving, like the rest of theology in general, as an expression of loving our God with all our minds, apologetics specifically serves to show to unbelievers the truth of the Christian faith, to confirm that faith to believers and to reveal and explore connections between Christian doctrine and other truths” - taken from his excellent book Reasonable Faith.
Peter wrote that we are to in our hearts "set apart Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience, so that those who speak maliciously against your good behavior in Christ may be ashamed of their slander (1 Peter 3:15-16).
This will include rebutting and refuting claims against Christianity as well as providing reasons for the plausibility of the Christian worldview.