Use cases of question and answer sites

Quora

Quora is strongly geared towards open-ended questions. Yes/no questions are not preferred.

Answers.com

For questions with factual answers. Yes/no answers are encouraged on answers.com. Not peer-reviewed like Stack Exchange and Stack Overflow which we will get to later.

Yahoo Answers

Shut down in May 4th of 2021. From April 20th until then, all existing questions and answers were read-only.

Yahoo! Answers was geared towards for questions with factual answers like answers.com. Yes/no questions will be accepted.

Stack Exchange and Stack Overflow

Comparable to answers.com, strictly questions with factual answers. Also for answers to technical issues. Answers are also reviewed by multiple people.

Separate subdomains for each subject or topic, don’t really cross between them.

Reddit

Made up of many communities for different subjects. reddit.com/r/answers is for factual answers, just like answers.com, whereas reddit.com/r/askreddit is for open-ended questions and more comparable to Quora. reddit.com/r/DAE is for asking “does anybody else” and “Am I the only one” which are not encouraged on Quora.