Tagging members lets them know that you have asked them a question, responded to a comment or query. You can tag another member or several members by using the @ sign followed by the username. A pop up box will appear with the username that you are typing out and if it is the correct user you want to tag then click on the box. The rest of the name will automatically appear. This will send an alert to the person that you have mentioned once you have posted the message. The alert will appear in the drop-down menu.