Short essay on dualism, idealism, & materialism as concerns Q: What is a table?

[Mudhammam]

Not going to read the OP I'm afraid, too long and full of philosophical musings. But for me something is a table if it performs the function of a table. That is, it's stable, you can put stuff on top and sit down by the side with your legs underneath it.

Do you really need to add anything more than that?

That sounds like a pragmatic nominal definition of a table.  But my concern is what is the "stuff" of a table -- does it exist independently of my experience?  What does it mean to speak of something that in principle is not experienced (namely, the table as it exists unperceived)?  Can I know that anything exists in such a way?  What distinguishes "impressions of tables" from "ideas of tables" -- not merely in the sense that in perception a table appears more vivid while in thought or memory it is fuzzier and more abstract -- but what does it mean for something to be concrete vs. abstract and how do these relate to each other?