Instant IDE is a stand-alone piece of IDE software that can be independently installed on any website. While the Instant IDE Manager Plugin is a WordPress Plugin that not only includes the Instant IDE software, but provides useful features that allow you to fully manage Instant IDE. From one-click installs and uninstalls to direct .htaccess file editing, the Instant IDE Manager Plugin helps make Instant IDE that much more accessible to the average user and that much more “Instant” to anyone using this powerful dev tool.
So just to review:
Instant IDE = A stand-alone, fully independent web development environment.
Instant IDE Manager = A WordPress Plugin that not only includes the Instant IDE software, but provides useful features that allows you to easily install and uninstall Instant IDE, among other things.