Difference between Skin and Html Template category

Hi everyone!
I uploaded my Item in themeforest Site Template category.
At first I got feedback with “soft reject”, so I fixed the errors and I resubmited the Item, then I received an “hard reject” with this comment:

“This item would be redesigned as a Skin and submitted to CodeCanyon. Please see examples under the Skins category on CodeCanyon.”

This is the demo URL : https://socialyte.codeplus.it/

So what is the difference between Skin CodeCanyon category and Site Template Themeforest category?
And why my item is categorized like a Skin element and not like a Site Template?

Thanks in advance