Apologetics is the study of Christian theology and philosophy. It studies how to answer the the tough questions one might have about God, The Bible, or Christianity such as "What is some historical evidence backing up the life of Christ" or "How was the bible inspired by God" or "How is Jesus the Son of Man yet also the Son of God". All of these questions will be easily answered by reading "Systematic Theology" by Wayne Grudem or "Know why you believe" by Paul Little. Another book that may help is "Evangelism for the Tongue Tied" by Chap Bettis.