As the Boruto anime moves forward we begin to talk about his eye which has been making an appearance as of late. While Boruto think it is the Byakugan (and remember that is his best guess as it is the closest thing he can think of as it is what he knows.) This will include some spoilers so be warned. AGAIN SPOILERS AHEAD.
We can see it is something but what is the Tenseigan? Well it is the eye jutsu from The last Naruto The Movie used by Toneri. Which is why he gives makes a small appearance in Boruto dream. Remember the manga is different.
From what I can see it is similar to the Rinnegan basically acting as the highest form similar to the Rinnegan and Sharigan. For those who have not seen it I will post a few videos of Toneri did with it. We still need to see what Boruto can do with it. Remember he has that and the mark so the future Boruto from what we have seen we are getting a taste of half of his power.
As always thank you for reading.