I've written ORM's, I don't need them explained to me, and no all ORM's don't try and hide the database, that's just one pattern. Others like ActiveRecord simply try and make life simpler without complete hiding behind so much magic you can't figure out what's going on. ORM's abstract the database, that's not the same as hiding the database.
Except for the times when they load all columns into memory and then you programmatically discard almost everything because you really just needed Person#name.