icm/HTTPS/verify_client is a SAP Parameter attribute which is used to control Require SSL Client Certificate information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter specifies whether or not a client must produce a
certificate. There are three verification levels (0-2):
0: No certificate is required and the server does not ask for one.
1: The server requests a certificate from the client. If the client does
not send a certificate, authentication is carried out by another method,
for example, basic authentication (default setting).
2: A client must send a valid certificate to the server, otherwise
access is denied.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.