What are the differences between type B message format and EDIFACT message format?
There are many types of messages which are used very specifically within the aviation Industry and TypeA and Type B are the most notorious ones.

Its not the message format that differentiates them , its the characteristic message delivery and response that does.

Type A - Expect immediate application response, have timeout handling in place at the application level, delivery is not guaranteed and could expect loss of messages. EDIFACT is one of the well known industry accepted and following TYPE A message formats..

Type B - Guaranteed delivery and will make anything and everything possible to deliver the message . Does not expect an immediate response back.

Regarding the format of the messages, the type A message formats are governed by PADIS ( PASSENGER AND AIRPORT DATA INTERCHANGE STANDARDS MESSAGE STANDARDS DOCUMENT). It does differ for each applicaiton( reservation, ticketing, DCS etc). Here is a sample one for PNRGOV standards.

https://www.iata.org/iata/passenger-data-toolkit/assets/doc_library/04-pnr/PNRGOV%20EDIFACT%20Implementation%20Guide%2013_1.pdf

For TYPE B , always refer to the AIRIMP documents which governs the TYPE B mesasge formatting..

Here is a sample of the same..
ftp://ns.tais.ru/pub/doc/AIRIMP34.pdf

Thanks,
Jothi