We have covered some of the individual elements in separate questions here on Meta, but I would like to collate the relevant information about what russian.stackexchange.com is or is not. This could well be then linked to from the FAQ. I'll start here by summarizing what I found in other meta question. Do add as answers anything else of note.
A place to ask questions related to the history of the language. If you want to know how a certain side of the language evolved, this would be a good place to raise it.
A place to ask questions about word differences or usage. If you are learning the language or simply have doubts about the difference between two or three or more similar words, ask a question here.
A place to ask questions about the Russian grammar. If you are unsure about verb tenses or noun declensions, this would be a good place to ask.
A place to ask questions about word structures. How/why/where/what specific prefixes, suffixes, endings or word roots mean, constructed, assembled, etc. should be asked here.
Russian.stackexchange.com is not:
A place to request translations to or from Russian. You can ask whether a particular translation is a good way to convey the meaning, but not "how to translate X from A to B".
A place to have a discussion. This is a question-and-answer site. Your question should really be that - a question, that calls for answers. Open question that solicit discussion, such as "What do you think about X?", are not a good format.
A place for flame wars. If you dislike a particular member of the forum and want to express your thoughts, take it outside the forum. Don't blame, swear at or try to humiliate other members of the site in your answers. You can downvote the answer if you believe it is not correct or useful.
A place for retaliations or voting wars. Do not downvote somebody's answer just because they may have downvoted yours. Votes should be used to show whether answers are correct/incorrect and useful/useless. Downvoting somebody's answer to promote your own is also highly frowned upon.
A place to get others to do work for you. Your question should contain some thoughts. There are questions that can be answered with a very simple/short web search - so do that search and get the answer. If you're still unhappy and need more explanation, then post a question on RSE, but indicate what you have found so far and why you are not happy with that.
A place for free advertising. Do not post any kind of covert advertising on the site - in any form. Such posts will be quickly deleted anyway. Question "why is product X so good?" will most likely be construed to be advertising.