You may have heard the term Christian apologetics and been unsure what exactly it was. It is an old term that doesn’t mean saying “I’m sorry” for Christianity. I finally came across a concise explanation in a book about early Christianity:
Referred to by scholars as the classic Christian “Apologists” (from the Greek word apologia = “defense”), these writers not only responded to accusations against Christians; they also attempted to advocate and defend vigorously Christian beliefs in the larger intellectual world of their time. 
Christian apologetics, defenses of the faith, are still being written. C. S. Lewis is a well-known example of a 20th-century apologist.
 Larry W. Hurtado, Destroyer of the Gods: Early Christian Distinctiveness in the Roman World (Waco, TX: Baylor University Press, 2017), 4.