From The Apple Wiki
Original author(s)Apple Inc.
Developer(s)Apple Inc.
Stable release
1.0 (410)
(latest known version)
Operating systemmacOS
Size51.1 MB (51,094,091 bytes)
Available inEnglish
LicenseClosed source

CarDisplaySim is a program used by Apple engineers to test CarPlay. The program is meant to be used with InternalUI devices, so connecting a production device yields no results.
Newer versions of CarDisplaySim do not display a ui, until a device has successfully connected to it.