In harmony with the Great Commission in the Matthew 28:18-20, Your and my responsibility as a Christian is to make disciples of all nations, baptizing them in the name of the Father, the Son, and the Holy Spirit, and teaching them to observe all that He (Jesus) commanded us. We are commissioned by the Living God to share the Good News of Kingdom of Heaven being come down to the earth. We are commanded to keep the heavenly law – Love God and love your neighbor – and make known Christ as our Savior.
You share the story of Passion of Christ to someone. You proclaim the truth from the Scripture, the inspired Word of God. He may or may not simply believe what you say. He may have cantankerous or belligerent disposition about Christian faith. He might want to know what you just shared with him could be verifiable or not. He may storm you with questions regarding the very existence of God and the authenticity of the Bible.
Now, you simply cannot avoid these legitimate questions when asked sincerely. Thus, your is the responsibility to present your concrete arguments and reasoning rationally what you believed is to be universally true by grounding your reasons solidly in the Scripture.
Apologetics is a discipline dedicated to the defense of something. The term “apologetics” is derived from the Greek word “apologia,” by which means “to defend” or “to make a defense“. In this sense, apologetics is the tool to give a reasoned defense for what you believe to be true, hence your faith can be attested and proved rationally.
“But sanctify Christ as Lord in your hearts, always being ready to make a defense to everyone who asks you to give an account for the hope that is in you, yet with gentleness and reverence” 1 Peter 3:15 NASB