Is my supervisor making things clearer or confusing?
When and why would I, as a supervisor, ask students "What's this?" rather than just telling them (assuming that "this" is something I already know about)? The most likely situation is that I can't tell whether the student understands the relevant definition. If I already knew that the student didn't understand the definition, then I'd explain it, but if I'm unsure about the student's understanding, then I might ask questions intended to show me what the student knows or doesn't know. The student might view such questions the way you did, as "making things doubtful", but that wouldn't be my primary intent. (It might be a good side effect; if the student has a wrong idea, causing doubt about that idea might be a good preface to explaining the correct idea or to sending the student to study it.) 

I'm worried by the last part of the material you edited in at the end of the question, the part about multiple definitions of the same term, assuming the wrong definition, things not defined in a good way, and a confusion of concepts. This sounds like a recipe for a disaster. I would recommend that, as soon as you see two genuinely different definitions of the same term, you try to determine whether they are equivalent. If they aren't, or if you can't decide whether they are, then ask your adviser to explain. Are there really two different concepts with the same name? If so, which interpretation of the name should you use? Getting the definition clear is necessary before any other work involving that concept; anything built on unclear definitions will be unclear (if not outright nonsense).