The term "virtual" experience is normally used in the context of "virtual reality", multi-sensory immersive computer simulations that are so close to reality that it seems almost as if they are real.
There are two ways you can tell them apart, context and limitations.
For context, many video games are increasingly attempting to provide an immersive experience, but you know that you have entered into the experience by turning on your computer, and even if manufacturers can provide multi-sensory feedback, assuming you are reasonably sane, some part of your mind should still be aware that you are not actually a gnome warlock flying around on a dragon.
For limitations, current virtual reality technology is not good enough to accurately simulate actual experience, and therefore you are aware, via technological limitations, that it is not real. As the technology improves, the distinction will increasingly be purely contextual.