Ephesians 4:11 says, These are the gifts Christ gave to the church: the apostles, the prophets, the evangelists, and the pastors and teachers. The gift of evangelism is the God-given gift of being able to explain the gospel to non-believers in a way that leads them to faith in Jesus. The original Greek word means a missionary, or someone who brings good news. Thayer's Greek Lexicon explains that evangelists are those who preach the good news about Jesus to non-believers who are not New Testament Apostles. All of us a called to share the good news about Jesus, but some people are particularly gifted in this area.
Apologetics means being able to defend your faith. All Christians, including teenagers, should be able to explain what they believe and why to anyone who asks. You don't have to go to Bible College to do this. Here are some useful books that you can read:
10 Questions Every Teen Should Ask (and Answer) about Christianity by Rebecca McLaughlin (I've just finished this book)
The Case for Christ (Student Edition) by Lee Strobel
Don't Check Your Brains at the Door by Josh McDowell and Bob Hostetler.
Short and sweet inspirations for Christian teen girls.