For me, the concept was that we are filtering out most of what happens in the shared environment (in order to not being overwhelmed), that our mental mechanisms are rather imperfect (most of people are absolutely sure that they have flawless tools, and the entire universe is completely comprehensible) and that different people could have incompatible inner representations of the very same phenomena.

Btw, the flawed mental apparatus as a reason to hypothetical inability to comprehend "the true nature of reality" is one of the basic premises of thousands years old Indian philosophy, which emphasizes subjectivity.