People always say “there’s no such thing as a stupid question”, but most of the time – the people they say that too don’t believe them and decide “I’m not going to ask that because I’ll sound stupid”.
I think that most of the time, when someone “doesn’t understand” – it really means “I’ve come up with a mental model of how this works, and the new information you’re giving me doesn’t fit into that model”. The best way for a teacher to help get you on track is to understand your current mental model. The best way for the teacher to figure this out is for you to ask questions.
It’s like being lost and calling and asking someone for directions (before we had GPS and mapping apps). They can only give you directions if they know where you are coming from. If you tell them “I’m looking at a Dairy Queen right next to a Taco Bell” (and they’re familiar with the area) – they can say “Oh – you turned left instead of right. Here’s what you want to do…”
If you just keep saying “I’m lost” (or worse, not saying anything) – it’s much harder for someone to help get you back on track.