If I am served a summons but I am not the named defendant, do I still file an answer with the court?

Only defendants to an action need to answer the complaint.  If you are not a defendant, you have no reason to answer, and the plaintiff has no reason to serve you, unless delivery to you was the plaintiff's way of serving the actual defendant.  If, for example, you live with the defendant, delivery of the summons and complaint to you at your shared residence would be good service on the defendant in some cases, and he/she would be obligated to respond to the summons. I just want to add that the above answer applies if you're really not a named defendant, not if you're the defendant but they misspelled your name, forgot to add "Jr.", or something similar.  That kind of excuse for not responding to the summons and  complaint is unlikely to get you far.