eu/iwb/server_mac is a SAP Parameter attribute which is used to control Info Workbench: HTTP server for Help on Mac platforms 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 .
The parameter specifies the host name of the HTTP server for Extended
Help when Macintosh front ends are used. You only need to maintain this
parameter if help type 2 (PlainHtmlHttp) or 4 (HtmlHelpHttp) is used.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.