These mean more or less the same thing. I know that some people may not be familiar with the canonical term for extract/grain hybrid brewing (partial mash brewing), but if we keep both it will confuse searches down the road.
Extract plus grains is not the same as partial mash. Extract plus grains refers to brewing with extract as the primary source of fermentables while steeping the specialty grains that do not need mashing to extract their flavor and sugars. In extract plus grains brewing, no mashing is carried out.