As Anil Seth observed, when people are in general agreement of what it is they experience, we call that reality.
Empathy is the ability to place yourself into someone elses’s reality.
Ever winced when watching someone hurt themselves, but you are just observing? That is your mind producing the same biochemical action potentials as the person actually getting hurt.
Note that at best people can only experience a very narrow sensory band of the total wave frequency spectrum . But we can build very sensitive detectors that can inform us of those parts of reality we are unable to physically experience.
There are many animals and organisms that are sensitive to a much greater frequency band width than humans. Each species that’s alive today has an evolved special survival skill that allows it to survive, if not thrive, in today’s environment.
The survival skill speaks directly to the reality these species experience and is proof of its existence for that species. People living in a fantasy are rarely successful survivors.