Reality is an especially slippery word; its meaning may be interpreted in many different ways. The most common conception of the term, as you could easily find on a search engine, is “The state of things as they actually exist, rather than as they may appear or might be imagined.” Yet the word is not also used in this way.
We can say that we “create our own reality”, and, depending on the definition, this can be considered to be a true statement.
However, we can also say there is only one true “reality”, and, in a similar fashion (depending on the definition), this also may be considered to be true. In this sense, one would assume that there is only ONE “reality” because it is the one founded on truth: that which is factual or indisputable (but not necessarily objective and measurable, it may include metaphysical elements). The nature of God is, at times, simply called “Reality”.
There is also the concept of reality as “one's own reality”. This may either refer to a solipsistic conception of the individual acting as the sole arbiter of truth, or it could be part of a belief in the divisibility or relativity of “reality” itself, such as when we refer to “alternate realities”. This version of the word defines “reality” in a relative fashion – as something either fundamentally subjective, or relevant only to a part or portion of existence.
There is also the concept of “imaginal reality”, where a continuum of concepts exists independently of the physical world, or “virtual reality”, a term that implies that reality is a subjective principle, amenable to manipulation or substitution.
I would posit that the word “reality” ought refer to the absolute Truth of existence, its underpinning or ultimate actuality (necessarily transcendent and yet immanent without limit), rather than being used to suit lesser ends.
In the case of multiple “realities”, I assert that it would be best to posit a “multiverse” of universes with potentially divergent principles (even though this is a corruption of the original concept of universe, this is already a common usage), all of which are contained within the one indivisible Reality.
Any cosmology that rejects the ultimate interconnection or subtle continuity of all existent things is fundamentally flawed, because every extant “thing” must, of necessity, have a matrix or context in which to occur, and this context must be continuous (like the relationship between space and the galaxies within it). This is relevant even if there are many different universes which may not have the exact same rules. The universes must have a co-extensive matrix. This may be taken as a preposition of faith, I suppose, as it would be difficult to prove.
The large question that this conception of Reality brings up – what the nature of Reality actually is or may be – that is another issue to consider.