Objects are sort of like things, but aren't quite the same.
One of the main questions goes as follows: what are objects and what can we know about them. By object I mean that which is obseved and acted upon by a subject. That is, I am treating things as if we have a subject-object dichotomy and can distinguish between the two.
If everything besides the subject is an object, then we are mere steps away from a type of solipsism. One could allow that other people/humans are subjects as well, but where does one draw the line?
Of course, some people get a bit up-tight when other people (individuals or, especially, groups) are treated as objects.
The question is, what can we know about the world around us? This is not so much a question of our psychology as it is of our ability to perceive the world. We have 5 senses: touch, taste, sight, hearing and smell - 5 ways in which we experience that around us. To what extent can we trust our senses?
The classic example given here to explore this questions is as follows: imagine that you are wearing green-tinted glasses - everything you see is colored green. Yet, you can remove these glasses and see things "normally" again. Imagine instead that your eyes had a green lens, so that everything you observed was green, and yet you could not remove these "lenses" - to you, the world would be all green, and you would take these various shades of green to be properties of the objects you observed.
Similarly, how can we know that what we observe by way of our eyes, for example, gives us an accurate representation of the object itself - das Ding an sich? We obviously cannot. How do I know that when I see blue that my neighbor sees the same shade of blue, or even blue at all. Sure, I can point to they sky and say, "The sky is blue", and my neighbor can respond "Yes, the sky is blue" - however, do we mean the same thing by blue? Perhaps, perhaps not. As of yet, there is no way to tell. On the other hand, does it matter? We both agree the sky is blue, grass is green, etc. In practical matters, it does not matter. However, it does help to illustrate that those bits and pieces of sensory input we receive by way of our eyes, ears, nose, etc. do not tell us about the supposed object we are observing; our experience is always mediated.
If we cannot trust our senses, and in our use of language, etc. we cannot communicate directly with our neighbors (the term I will simply use for those with whom we come into contact), then how can seek to reach a common understanding? Some might argue, we are all humans, hence we have the same senses, and hence we observe things in a similar fashion. More extreme arguments might go along the lines god created us all, so by way of god, we can trust our senses - not a very convincing argument to me, but oh well. As for the "we're all humans" bit - it's not entirely convincing, either. After all, we are all humans - are we not? - yet drugs can alter our ability to perceive the world, we all have different intellectual capabilities, some people are blind, others deaf, and others mentally ill? Even if we shove these "marginal" cases to he border, I really doubt we can treat "the rest of us" as somehow "normal" and hence "the same" to the necessary extent.
The question of establishing an absolute, universal and/or "objective" reality, while it is a question primarily of what we can know, and occasionally a question of "what is" (ontology), its major importance for "us" is in the realm of ethics. Ethics (and morals, but I'll use the term ethics, even though I don't believe the terms to be synonyms) rely on human interaction; without "others", why would we need "ethics" or "morals"? However, since we take ethics to be something universal - or at least, we want to be able to apply them across the board, no? - the necessary subjectivity of the subject and the inability to establish an objective reality hinders most attempts to do this.
To me, then, this connection between aesthetics (perpection), epistemology, and ethics is both interesting and central.