Full Idea
I think it should be recognised that there are two fundamentally different types of explanation; one is of identity, or of what something is; and the other is of truth, or of how things are.
Gist of Idea
We explain by identity (what it is), or by truth (how things are)
Source
Kit Fine (Guide to Ground [2012], 1.11)
Book Reference
'Metaphysical Grounding', ed/tr. Correia,F/Schnieder,B [CUP 2012], p.79