What is the Orthodox Church?

Yes, "Come see and hear (and smell and taste and touch)" is always a great response. This helps you to discern between those who simply want to enter into a philosophical argument and those who are truly seeking. I also sometimes say "it is the New Testament church", and then share The Creed (Symbol/Statement of Faith) with them. Also, ask your spiritual father if he has preferred literature to share with enquirers. Depending on the person and the guidance of my spiritual father, I prefer to share "The Orthodox Way" or "The Orthodox Church" by Archbishop Kallistos (Timothy) Ware,one of the Clark Carlton series (depending on if they are protestant, catholic or "other") or any one of a number of other suitable books/pamphlets. Most important, when someone asks about your church, it's a great time to ask your spiritual father to hear your confession, and then partake of the Holy Eucharist. With such preparation, you will be well-equipped to share your Orthodox Christian Catholic and Apostolic faith with those who have ears to hear. Lord Have Mercy!