If you're wondering what an emblem is, you are correct: Until now, there's no such thing as emblems. Furthermore, there are no cards that create emblems ... or at least, there won't be any such cards until the Oracle update goes live this Friday. At that point, there will be one—and only one—card that can create an emblem: Elspeth, Knight-Errant.

...

What Elspeth really wants to do is create a pseudo-enchantment with a static ability that works for the rest of the game. So ... an immutable enchantment. One that can't be destroyed, or stolen. Something like a Vanguard card that you get in the middle of the game rather than at the beginning. An object with an effect that hovers over the rest of the game. We can do this. We can invent emblems.

New Elspeth, Knight-Errant wording

[+1]: Put a 1/1 white Soldier creature token onto the battlefield.

[+1]: Target creature gets +3/+3 and gains flying until end of turn.

[-8]: You get an emblem with "Artifacts, creatures, enchantments, and lands you control are indestructible."