If you've asked a question, you'll have the option to mark any reply as the Best Answer. Marking something as Best Answer gives the question a green checkmark to show others the question has been solved and helps others to find the answer to their question.
Best Answers also help the author of the answer to rank up in the community. They're a nice way to say "Thanks" to the person who took the time to post. 😄
To mark a post as Best Answer, just scroll to the bottom of a post and click the button Mark as Best Answer. That's it!