Basically, if some helped and gave you the answer to you problem you can thank him marking the answer as correct.
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Greetings,
I think that's very important that all Atlassian Answers Users, especially new ones (including me), take conscience about this matter.
Marking an Answer as correct is very helpful for all the users because, before asking a question, I think we all take a time searching if the answer to our issue resides in a question already asked.
Only to consider this.