Culture is what sets a group of people apart from other groups. There is American culture, English culture, etc.. Your culture is made up of your values, language, music, symbols, humour, customs. When you go to another culture you notice the difference in these things.

When Christ enters you life, all these things begin to change dramatically. That makes us uncomfortable with the secular culture of our non-Christian friends and the people around us. At the same time they are feeling more and more uncomfortable with the cultural changes happening in us!

This means that if you are going to communicate Christ to them, you must think cross-culturally. You must talk in terms they will identify with. You must talk about how Christ will meet them in ways they care about. They must want to know Christ. So in your witnessing, THINK about the culture of the people you are talking to.