CrossBox 1

Classic CrossBox Server ("CrossBox 1") runs on Mac as a standalone application, and is used solely for building and debugging Cocoa apps on Mac, iOS and tvOS, from a Windows-based development environment.

You do not need CrossBox 1 if you are using Fire, or if you are not doing Cocoa develoopment. Also, CrossBox 1 is deprecated in Elements 10 in favor of the new SSH-based CrossBox 2, which does not require a dedicated server app to run on Mac.