You are going to need to explain this with much more detailed information. I have no idea whether you are asking for a description field that an administrator sets per tab per category or what? Is this displayed only on the EDIT view or Item View or both? There is just too much info I need to even understand what you want.
Added in fields to store Tab descriptions. These descriptions are displayed on the Item Create and Item Edit forms only. As shown in the first image image below, you simply enter in a description (plain text or HTML) for a tab and it will the display above the editor for that tab (as seen in the 2nd image below).
NOTE: These will NOT display on the public Item page. This is for use on the Create and Edit views only.