What these philosophers are pointing out is that perception is reality. Your perception is your reality; my perception is my reality. What is real then?
Reality is three fold. Reality is what I perceive and what you perceive, but it also is what society agrees to call reality.
I am colorblind. Blue and green are indistinguishable to me. I would call those colors blue. My wife is not colorblind. She would call some of my blue colors blue and she would call others green. We are both right. However, if the majority decide that some colors are blue and some are green; for them, I am considered colorblind. And to that point, each member of the majority would still have their unique perception of what color is blue.
As a practical matter, I act as if I am colorblind. I ask my wife if my socks are correctly paired by color. Still in my perception, and therefore in my reality, they all look the same color.
If there is a real reality, it cannot be known since the only way to know is through perception. If we can internalize this concept, we increase our effectiveness in dealing with our world and each other greatly.
To be continued.