"You could create an alternative universe where an hour there is a minute in ours." - Alex in Wizards vs. Vampires on Waverly Place.
Alternative Universes, also referred to as Weird Alternative Magic Universe, are parallel dimensions that cover the entirety of reality: in other words, includes Earth, the Wizard World, the Afterlife, Magic Limbos and any other dimensions.
These universes usually are copies of our own but tend to differ in certain but quite crucial details.
Travel between Universes[]
The only known way to travel between universes is magic. The other way to travel between universes is by using an extremely powerful enchanted magic mirror, however it will lead to a reverse universe.
Creation of Universes[]
Very powerful supernatural beings such as Wizards can create alternative universes through spells, as Alex did in The Movie. These universes might be dangerous, specially if they deal with the time stream. Universes where a person is not supposed to exist will slowly begun to strip that person of his/her memories and then erase it.