Q:

What is a good forum for math discussion?

This forum is inadequate for my needs, because the question/answer format is too restrictive.
I need an online forum were I can make questions, and discuss the answers. I want to contact people with good math level.
I'm not a student, but not a mathematician either, so I may make naive questions which are not precise enough for this forum standards.

A:

I'm not a student, but not a mathematician either, so I may make naive questions which are not precise enough for this forum standards.

I mainly wish to address this issue. I do not think that anyone is not capable of asking sufficiently precise questions. At the very least you would have an informal question and also know that it is informal, in which case it may be appropriate to mark your question as intuition or soft-question. Besides that, you can easily ensure that every symbol you use has been defined. This is the most frequent issue that makes a question "unclear" or "lacking context". Imagine if someone asks:

How to prove that $x^2 \ne -1$?

My first response is:

What is $x$? Is it an elephant?

In most cases, the person who asked did not actually state everything that he or she did know, and it is not even possible to guess it. Here are two possible correct questions:

How to prove that $x^2 \ne -1$ for every real $x$?

How to prove that $x^2 \ne -1$ for every $x \in \mathbb{F}_p$, for any prime $p = 4k-1$ where $k \in \mathbb{N}$?

If you put in effort into making your question precise, but find that you are unable to, then you will nearly always find that one of the following holds:

You actually do not know the concepts you wish to ask about. In this case it may well be better to ask about the concepts rather than blindly charging ahead with a question whose meaning you are not even sure about.

You are looking for some mathematical structure that you believe exists but you have not come across before. If you can pin down precisely what are the properties of the structure you wish to find, then it would be a precise question and fit for the site. If you cannot, it may be that you are chasing some vague intuitive notion, so you should describe mathematical motivation and also tag your question appropriately.

A:

You can try on reddit. If your questions are interesting enough and do not resemble homework, you can try on the subreddit /r/math,  otherwise /r/learnmath is more permissive.

A:

The Art of Problem Solving forums are a really good resource, and most of the people there are pretty high-level.

