This term isn’t referring to the overall quality of the flour but the amount of gluten in the product. Gluten is a protein composite which gives elasticity to dough and helps it rise. If baking bread or dense cakes, the recipe is likely to list high grade flour to ensure bread rises and is of the right density. Standard flour is better for light pastries and cakes, which call for a more delicate texture. Always use the type of flour your recipe demands.