Suggested Answers
When answering a question, a user can click suggest as answer to indicate their confidence in the accuracy of their response. This functionality exists on the first response as well as any of the later responses to the thread.
Suggested answers are highlighted within the thread and the author of the question (as well as anyone else who had the question) will be notified that a potential answer has been provided. The author and others who shared the question can then review the answer and (possibly) verify it.
Verified Answers
Any reply (suggested or otherwise) can be verified as an answer by the author of the question or anyone who also had the question. Marking an answer as verified lets the answerer know the value of their response, and generally communicates that the author is satisfied with the answer to the original question.
Rejected Answers
The author of the question and anyone who also had the question can also reject answers by clicking reject answer below the response. This simply indicates that the answer is not satisfactory and invites others to offer alternative responses.