Parallel Universes?

I heard that we have parallel or alternate universes, is this true?
If it is, how can we prove it?

The concept of parallel universes isn't true or untrue... it's a concept. We have yet to test any of it. It's simply an idea at the moment.

We currently move in 3 dimensions.
The fourth being time.
The question posed to many theorists is what would a 5th dimension look like.

Well, if the second contains intersections of the first... and the third contains intersections with the first and second, and time intersects all three of those dimensions... then whatever dimension is the 5th dimension would have to intersect with everything, including time.
This means that the fabled 5th dimension would have to contain variations of timelines and events.
This infinite number of variations of every possible timeline is what we tend to referr to as a paralell universe... or often called an alternate dimension, depends on who you ask really.

Like I said, it's a concept, not a reality yet, we don't have the means to test, nor disprove any of it... so it shal remain the work of science fiction for now.