.gif itself spoils nothing for anyone really.
Manga people will know what it is.
People who've watched anime up to this 129th episode, won't know what it really is and how an Uchiha acquires it.
This is Sasuke's flashback, and the continuation in episode 130 reveals everything behind that eye (because it contains, and is in core tied to a lot of STORY that's related to Sasuke, Itachi, Uchiha, etc.).
Basically, the explanation of the eye, puts the entire 129 episodes into a different perspective, but I won't say anything about it, because that's spoiler material.
Eye itself is harmless
