What excactly is the difference between kufr and shirk?

As far as I understand until now, shirk is to "worship" anything other then ALLAH, were the term "to worship" is a matter of believe and circumstances (otherwise any living soul would have the sin of shirk no matter how hard they try). Kufr looks more like an ethnically aspect, or otherwise, not worshiping anything, not having any deity at all. Please clarify. ---- With my low status of reputation points I am not allowed to leave comments and will stay away from this site, as I cannot do any good and would not misuses answers in place of comments. Have a nice day.