What is the difference between Reformed and Presbyterian

I feel like this is a dumb question, but maybe, just maybe, I'm not the only one confused by this. Maybe if I'm willing to stick my neck out and look stupid, the answer will be here for those poor confused saps who come after me. It seems like I often hear the terms *reformed* and *presbyterian* being used interchangeably. When I'm speaking about the presbyterian church, or rather, the reformed church, or... I often stumble over my words because I feel like I'm probably saying the wrong thing. I know that in a technical sense, *reformed* refers mostly to the theology and *presbyterian* refers mostly to the church government (or maybe I'm wrong about that too), but, in every-day parlance, what do you call a church who follows in the tradition of John Calvin? Surely you can't go around calling them churches-that-follow-in-the-tradition-of-John-Calvin. It's a bit of a mouthful. If I call them Presbyterian churches, will someone think I'm foolish and think that I don't know what I'm talking about? If I call them Reformed churches, will I be wrong? Is it just a matter of only usually being right? Does it depend on the denomination/association? What do Christians who belong to such churches call themselves? Do they call themselves Presbyterians? Reformed Christians? Calvinists? All three? None of the above? Am I going to offend someone by using the wrong term?