From Manta Wiki

Interactive or Real-time?

This has been a topic of some discussion. Several people maintain that interactive renderings software provides some degree of low latency response to user interactive. For example moving the camera using the mouse and then waiting a few seconds for an image would be interactive.

Along this line of thinking, real-time indicates that the renderer's latency in response to the user is so low that there is no waiting involved.

We use the terms interchangeably. (Mostly because all of the Manta logo graphics say interactive, possibly because somewhere along the line someone thought it sounded better.) Since Manta scales well on parallel systems, it is possible to experience both interactive and real-time performance on modest configurations.