Original: The Mathematics Subject Classification (MSC) is an alphanumerical classification scheme collaboratively produced by staff of based on the coverage of the two major mathematical reviewing databases Mathematical Reviews and Zentralblatt MATH.
Simplified: The Mathematics Subject Classification (MSC) system is an alphanumeric ordering system for categorizing or arranging mathematical topics, similar to how a library arranges or orders their books on the shelves. The system was invented by the American Mathematical Society based on two major mathematical publishers: Mathematical Reviews and Zentralblatt MATH.