Forums are very helpful area for discussion on any topic as well as provide backlink for the websitea along with this forums are the best place to share and spread any beneficial resource like any promotional portal with others.
According to new algo of google that google give values to quality forums posting and index them quickly. If you post quality posts on forums you have more chances to get quickly improved your keywords ranking. Keep in after Google recent algorithm updates there is no space for useless and low quality posts.
Forum posting is one of the most effective methods of SEO. It can help you to get good amount of quality backlinks to your website. It is also best way to increase your search engine rankings. If you do it in proper way than you can drive good traffic to your site and make your traffic stable.
What is "Query resolutions" (point 1)?
Backlinks ... only if the links have do follow.
Why I do forum posting?
Anyone ( real person ) can enter my link signature if it thinks that I helped him somehow.
Now real people can eventualy buy from you ... what you sell.