The org.eclipse.rse.core.systemTypes and org.eclipse.rse.core.systemTypeProviders extension points are defined in the plugin org.eclipse.rse.core. It enables new system types to be defined in the Remote System Explorer's New Connection wizard, such that users can define connections to systems of that type. For example, you might define a new system type of "Solaris" or "RedHat" or some other specific type of operating system. The reason to define a system type is to enable tools to be created, via the subsystem extension point, that are scoped so as to only appear for connections to systems of that type.
Defining a new system type is easy. You merely need to supply the name of the system type, and two icons - one icon for connections to that systems of that type, and another adorned icon that is used when there is a live connection to that particular system.
When you create a new connection, the Remote System Explorer framework will consult each registered subsystem extension point to see if it supports that connection's system type, and if so the extension point's subsystem factory class will be used to create a new subsystem within the new connection. Thus, when the user expands a connection in the Remote Systems view, only subsystems supported for that connection's system type are available.