i want know about EDI and b2b Scenario

Hi friends,

  I would like to know about EDI and as2 adapter.

  I am new to B2B project.

  1) How we know EDI stuture formate. example is EDI is EDI ANSciX12 or EDI Fact?

  2)Wht is pre requerments need Before  use AS2 Adapter.What kind of imformation we need( SAP pi Technical person project wise).

  3)Wht is MDN in AS2 Adapter.

  4)Mapping Please provide any one sample screen shot ( EDI field to FTP field)