Two mailing lists handle general questions about FreeBSD, FreeBSD-questions and FreeBSD-hackers. In some cases, it is not really clear which group you should ask. The following criteria should help for 99% of all questions, however:
If the question is of a general nature, ask FreeBSD-questions. Examples might be questions about installing FreeBSD or the use of a particular UNIX® utility.
If you think the question relates to a bug, but you are not sure, or you do not know how to look for it, send the message to FreeBSD-questions.
If the question relates to a bug, and you are sure that it is a bug (for example, you can pinpoint the place in the code where it happens, and you maybe have a fix), then send the message to FreeBSD-hackers.
If the question relates to enhancements to FreeBSD, and you can make suggestions about how to implement them, then send the message to FreeBSD-hackers.
There are also a number of other specialized mailing lists, for example FreeBSD-isp, which caters to the interests of ISPs (Internet Service Providers) who run FreeBSD. If you happen to be an ISP, this does not mean you should automatically send your questions to FreeBSD-isp. The criteria above still apply, and it is in your interest to stick to them, since you are more likely to get good results that way.