Set for the Defense of the Gospel
Some would define Christian apologetics as the practice of showing Christianity to be true. Others may define it as defending the truth claims of Christianity against all other opposing truth claims. In answer this question, it is best that we turn to the only source that can help us truly acquire a working knowledge the art and practice Christian apologetics: the Bible.
First of all the words apologeomai (defend oneself) and apologia (defense) appear 10x and 8x respective in the Greek New Testament. In order to understand the meaning of a word, it is always a best practice to see how it is used throughout Scripture. Once you establish the broad range of meanings for the word, and how it is used, you can then narrow the meaning down to how it is used in the specific passage under study.
What does this it look like when Christians are actually defending the gospel? Some would argue that it means going around debating the same person about the same issue repeatedly. Others would say that we should spend years debating specific atheists, engaging all the dozens, hundreds, or thousands of objections they can come up with for why they don’t believe the gospel. Some apologists will rudely accuse fellow believers of anti-intellectualism if they ever draw a line in the sand and refuse to be carried away with complex philosophical schemes designed to produce as many roadblocks to Christian faith as there are days in one’s lifetime. Jesus Himself commanded us not to cast our perils before the swine. He told us that if they don’t receive us, that we are to shake the dust off our feet and move on. Paul left off debating the Jews and turned to the Gentiles because they rejected His gospel.