Mike Rife
Ansys Employee

Hi agambhir_be20

See the MAPDL Help -> Material Reference -> Chapter 4.20.6 on CZM material for Contact.  If you are on the Student version you should be able to open the help from Mechanical.

The 'Mode' is the type of separation; mode 1 is normal to the interface while 2 is slip tangential to the interface (which your model seems to be, please correct me if I am wrong).  3 is a mix.