Buy for a hobby I don't understand

They're deep into something you know nothing about and you don't want to get it wrong.

They are serious about a hobby I know nothing about. Help me buy for it without embarrassing myself.

1. Explain the hobby to me in one paragraph: what people actually do, and what separates a beginner from someone committed.
2. Tell me the categories where buying is a bad idea, because the choice is personal, technical, or dependent on kit they already own. Be blunt: for many hobbies the answer is to not buy equipment.
3. Suggest the safe zones: consumables they will get through, storage and maintenance, comfort while doing it, reference material, or something adjacent to the hobby rather than in it.
4. Give me three questions I can ask them or someone who shares the hobby that will not spoil the surprise.

Do not recommend specific brands or models as current, and do not state prices as fact. Say where you are unsure, since hobby gear advice goes out of date quickly.

The hobby and what I know about their level:
Budget:

Finding a gift. Ideas built from what you know about the person: to a budget, made by hand, or needed tonight.