“Two sides of the same coin.” This common metaphor describes two ideas so intimately related that we can’t separate them despite their apparent distinctions. Evangelism and apologetics are two separate concepts linked in a very intimate way—so intimate that we are unlikely to employ one without the other.
Evangelism derives from the Greek word euangelion, which is often translated “good news.” The good news is the gospel of Jesus Christ—that He created us, died to pay the penalty for our sins, and made restoration between us and God possible. Evangelism is the act of sharing that good news (Matthew 28:19–20 and Mark 16:15). It does not take place unless we declare the person and work of Christ with words (though our behavior should complement our verbal witness).
Apologetics comes from the Greek word apologia, which doesn’t mean “to apologize” (as in our modern usage) but rather “to give a defense or reason.” Apologetics, as commanded in 1 Peter 3:15, only happens when we offer a defense for the salvation that we have in Christ.
Evangelism is not simply moral living, and apologetics is not simply defending a scientific model. Both of these activities must be centered on proclaiming Christ, who He is and what He has done, to fulfill the biblical commands.
As Christians evangelize, questions naturally arise about other related details, requiring apologetics. For example, Peter says that Creation, the Curse, and the Flood are important reasons for our confidence in God’s salvation (2 Peter 3:1–12). How can we really share the hope of Christ without explaining the reason for that hope?
Likewise, if we defend a position merely for the sake of argument, apart from a gospel-oriented purpose, we’ve missed the point of apologetics. Offering the hope of Christ and defending that hope are truly two sides of the same coin.
http://www.answersingenesis.org/articles/am/v6/n2/dual-necessity