Topic: Difference between TYPE-A and TYPE-B

Hi,
I have recently started studying 14443 protocol.
I need clarity on the below mentioned questions
   1) What is the main difference between TYPE-A and TYPE-B?
   2) Applications where TYPE-A and TYPE-B are used?
   3) What is the need for two TYPES?
   4) Advantages of TYPE-B over TYPE-A
   5) Is it possible to manage with just one TYPE? If YES then which TYPE?

Thanks in advance.

Muzik