What is the difference between Visa Application form A and Visa Application form B ?

Visa Application Form B is the supplementary visa application form. If you are one of the below categories of applicants, you need to fill in Visa application form B.
1. You are applying to work or study in China
2. someone else travelling with you shares the same passport
3. you are appluing for a visa in a country or territory other than the country of your current nationality