“Regular” paprika, also called American, sweet, basic, or Domestic Paprika, is what’s found in most grocery stores. It is gentle and earthy with an unassertive flavor. Regular paprika is never smoked. It makes a terrific backdrop for more strongly-flavored ingredients, so it’s often used as a flavor base in dry rubs or blends. It is often favored for its ability to deliver a bold, red color. 

Yidu, a town in Hubei province, China, is famous for its dried chili peppers. The region has a long history of chili cultivation and production, making it one of the leading exporters of dried chili peppers in the country. Yidu's dried chili exporters have gained a reputation for producing high-quality products that are in demand both domestically and internationally.

When substituting, use common sense. Cayenne pepper is as much as 50 times hotter than sweet paprika, so a 1:1 substitution wouldn't work unless you want some heat—the right substitution, in this case, would be 1/3 of a teaspoon of cayenne per 1 teaspoon of paprika. Make an informed decision, but also use thorough recipes that might suggest reasonable substitutions.