Emma can create portals of a variety of different colours and sizes - though currently she likes making pink and purple ones - and she can make them lead to any location and any time. She simply has to will a portal to form and it will do so, with no source of origin. She has once created a portal which led to an alternate timeline. She has also formed a portal to lead her to the location of someone who'd been deleted, but it is unknown where that would have taken her, as she was prevented from entering it by her brother. It could have possibly killed her.