Christian apologetics is a field of theology. This particular field is meant to defend Christianity against objections. Many say that Paul is the first apologetic for Christianity, defending it against attacks from the Greeks and the Romans. Other people categorised as a Christian apologetic include G.K. Chesterton (author of the Father Brown short stories) and C.S. Lewis (famous for The Chronicles of Narnia).
Most apologetics focus on one area of Christianity to defend. Some might defend miracles, while others might defend the Bible and its accuracy. However, to be a well-rounded apologetic, there are colleges and seminary programs meant to help upcoming apologetics learn what they’re doing. These programs are sparse in numbers, but they are offered internationally.