For a couple of months, the system will auto-close a topic when a post in that thread is marked as a solution.
The system will recognise this as the issue being solved and it will close the topic two days after the last reply, to avoid necro bumping in the future.
So, be very selective using this feature and only mark a post if it genuinely is the solution to the issue and not because you liked the answer. There are other features on the forum for such reactions.
The other upside is that other users who are searching on the forum for a similar issue can see the issue has solution.