Your eyes glaze over. Your hands get clammy. You shift your weight uncomfortably. Yes, someone is explaining how their car works and you have no idea what they're talking about.
I am often in the position where someone is talking about a part of a car that I don't understand for two reasons.
1) Friends refer to me as a "car guy," causing people to decide that they should tell me about how they got their 1978 Toyota Celica to pass CA smog testing.
2) I know absolutely nothing about how cars work.
Right now you're probably saying to yourself, "Raphael - you write for Jalopnik, surely you know how cars work!" Well, not really, which is why I get antsy when people point at some totally-normal looking tube in an engine bay and say something like,
Ha! The idiot who built this never properly flanged the inlet casing! Rookie mistake!