Ok so basically its Samsung's way of hashtagging posts. If u are familiar with #tags its the exact thing.
In case u are not let me explain. You can type individual words that describe the post u have just done. For example lets say u posted a pic of the sky in galaxy gallery, you can type tags such as sky, clouds, beautiful, cloudy, sunny. Any words that go with your pic and any words u like to add. Single words that describe the pic. Later when u post the pic u can see the tags u typed at the bottom. If u click on a tag example: sky , every pic/post that has been tagged with the word sky will appear to u so u can quickly find or browse any other pic with the same tag.
I hope that makes sense to u. Its a process of categorizing and organizing posts to be found later very quickly.
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