 Roughly and schematically, one fact grounds another when the latter obtains in virtue of the former: the former in some sense makes the latter obtain. It is a productive, generative relation. (See Bennett 2017 on the class of such relations, which she calls building relations. See chapter 4 of that work as well as Schaffer 2016 and Wilson forthcoming for discussion of the relation between grounding and causation.) Roughly and schematically, an entity ontologically depends on another when the former would not exist without the latter. Much, much more can be and has been said about these relations, but this is enough for our purposes. 