There's been a lot of discussion here, here, here, and probably elsewhere about scope. I want to address the other part of your question:
what this site assumes in relation to the asker's understanding/knowledge of Judaism
The site doesn't globally assume anything in terms of knowledge, but every poster has to pick a starting point. Unless the question makes it clear that the asker is a novice, an answerer's starting point usually assumes basic familiarity with tanakh, knowledge of common halacha as practiced today, and ability to recognize/follow citations in common sources like Shulchan Aruch. However, any assumption like that will be wrong some of the time and this site is for all who are interested, not just those who are already knowledgable, so it is not only ok but encouraged to ask for clarification. If you don't understand an answer in Hebrew, ask for a translation (or summary if it's long). If you don't recognize a source, ask what it is. If you don't follow an argument (because, say, the poster skipped some intermediate steps), ask for clarification. If you've heard something different, ask about it (or if you can support it, offer your own answer).
Nobody should ever walk away from Mi Yodeya thinking "those guys are too advanced for me".