AcceptedSolutions is a feature which enables you to highlight a response to your question/problem as the one which solved your query completely. It's a great way of thanking another member for helping you out, and for showing off that response as the best one.
If you have raised a question and someone has posted an answer or a solution, please make sure you mark that post as the AcceptedSolution. This achieves 2 things:
It marks your thread with a tick, which informs the wider community that the issue or question has been resolved.
It provides a direct link to the solution for anyone else who has the same problem. Just click on the 'tick' in the first post of the thread. You can check this out by clicking the tick in this thread.
Sometimes, AcceptedSolutions wont be available. This is either because the Community Team have turned it off, or that the Community Team have already selected the appropriatesolution. It may also be that you have been banned from using it due to abuse, in which case you will have been contacted by a moderator.