The above distinction was originally made by Richard A. Close in ‘A Teacher’s Grammar’ (1992). He had already formulated his ideas 30 years before, but published a revised version in the early 90ies. I believe the distinction to be quite valuable, even if not always clear-cut.
Grammar as fact concerns such aspects of the language that are non-negotiable if I want to be able to communicate with the majority of speakers of the language. Facts of grammar describe the essential regularities or rules of a language that define it and organize its meaning. Continue reading