Facebook tag is simply to let recognize the other individuals that they remain in the picture that you have actually lately submitted or you just want them to examine you photo. Okay let me inform you in detail-.
Meaning Of Tag In Facebook
1. When you publish an image on Facebook and also your friends in the image and also if you intend to allow your friend understand that he's in your picture than you can tag him.
2. When you tag somebody aware Facebook provide an alert concerning it as well as additionally include the post to their time-line as well as likewise other people whoever see his/her account can see the post as well on top of their account.( depends if the the personal privacy on public).
I hope it suffices to comprehend ...