Sorry if I must ask this stupid question, but I cannot figure out the meaning of the following user interface element in the backend (Magento 18.104.22.168):
Under any of
Catalog -> Manage Products -> edit product (Related Products, Up-Sells, Cross-Sells)
the first column of the search fields displays a check box (which is checked by default) and the value "Yes" is selected (the three values available are "Any", "Yes", and "No"). Furthermore when I click the "Reset Filter" button the checkbox disappears and the value of the drop-down menu which contained "Yes" changes to "Any". However I cannot figure out what the checkbox means, and also cannot figure out what the value of the drop-down menu below it from which it is possible to select "Any", "Yes", or "No" means. Could someone please explain to me the meaning of the checkbox field and the drop-down menu field?