They refer to either a copy of an object or a link to the direct object within another office suite application. Hmmmm, I suppose without getting deep into it, it's better just to try one. Open up Excel and Word in different windows. Now type something in a cell in excel. Manage both windows so that they can be seen at the same time on the screen and select the cell in which you typed text in. Now click/hold/drag the cell over to your new word document. If you did this correctly, you just created an "object" in your word document.
If you never see them active, chances are you don't use them. I wouldn't worry too much about them.