When someone attaches your Facebook profile to his post it is known as Facebook tagging. It is usually done to draw your attention to his post or include you in the post as it is about an event of which you were a part as well. people also tag their friends on posts that are meant for lighthearted fun as well. when someone tags you, Facebook immediately sends you a notification about it. If you allow the picture to be displayed on your timeline then even your friends are able to view it.