I am trying to get my head around the difference between the Apple products above.
To me, Apple VNC (or rather generic VNC clients) perform the same basic function as Remote Desktop implementations (Apple, Microsoft, Citrix, etc), and various Screen Sharing apps.
Also, it seems that Apple Remote Desktop can push scripts down to clients, and change some settings, much the same way as Apple Remote Management, and Remote Events seem to infer they do, by name.
Moreover, Remote Login is something (unless you wanted a shell) that you would do as part of a Remote Desktop / Screen sharing / VNC operation, no?
Best Answer
You are correct, VNC is a simpler version of Remote Desktop (note: Remote Desktop uses the VNC protocol in addition to adding a lot more features)
Remote Desktop offers more management features; ability to black out host computers screen, push updates, file transfers etc (think TeamViewer but by Apple). http://www.apple.com/remotedesktop/
VNC doesnt have any of these options, its just a simple way to access a remote screen.
Remote Login allows you to SSH to a remote computer (command line - you dont see the remote desktop)
eg You may want to run a command on a remote computer, you could connect using VNC and open terminal or instead you could remote login via SSH and run the command without actually interacting with the screen of the remote computer
Updated to include @Wheat Williams notes below