What is Class B income in Korea?

Excuse me, I'm somewhat confused about the tax system in Korea. Could you please elaborate on what is meant by 'Class B income' in this context? I understand that different countries have their own unique tax classifications, but I'm particularly interested in how this classification applies to individuals or entities earning income in Korea. Could you also explain how it differs from other types of income, such as Class A or other classes? Thank you for your time and assistance.