In SEO Question and Answer sites play important role. These websites are free to registration and anyone can come here, make account and can ask query/question.
Q/A sites are best sites to promote your product, service by giving answers to particular questions related to our product/services . In answer we can give link of our website. From this type of website we get high quality of backlink and it also helps to boost the rank in search engine.
Most of Q/A sites give DoFollow link, when search engine like Google come to this type of sites for indexing that time there bot index all questions and answers also. When anyone search query on Google search box that time it also gives Q/A sites in search results and when anyone link on link on SERP then from given link in Answer users will redirect to our website and traffic of our website will get boost