Display button [solved]. Where is it?

Please tell me what is this choice about? It is from user setting

Once you have activated this feature and you are replying on a thread, you will see a solved-button nearby the "modify the topics title" field below your text-editor (see the screenshot below). Clicking this button will automatically add [solved] to this topics title. The option itself can be found in "Users & Groups / Users / User Settings".

Thank so much! It so useful to mark solved many topics that be answered.

You are welcome!

And as your question seems to be answered, i'm going to close your thread.