All-Purpose flour is a "general" type of flour intended for any application. all-purpose flour can make cookies, bread, gravy, noodles, etc. and do a good job. All-purpose flour in many recipes is a simple substitution. You can even substitute barley for wheat flour in many instances for a different taste experience. Given however that whole grain flour has a richer more fulsome flavour and texture and contains more of the "berry", you will notice a difference in recipes calling for a white nutritionless starchy plain flour.
It really all depends on what you are using he flour for! Baking bread? or cookies? it makes a big difference in that case.