What exactly is a skewed dataset ? Like above, I'd like to know, what exactly a skewed dataset is.

The explanation from stats.se.com sounds to me more like what I call an imbalanced dataset?

What is the distinction?
In the context of the link, a skewed data set is referring to a dataset with a class imbalance problem. They are trying to build a classifier, but they have many more negative examples than positive examples. It's not a very precise term, but I've heard to used in this context a few times.