Couldn't find much online on how an interactive system is different from a time-sharing system, or the different traits of both.
My understanding of a time-sharing system is many people at terminals being able to use the system at the same time, and the CPU's aim is to maximise response time not CPU time (unlike a multiprogrammed batch system). The switches between jobs are very frequent, and users get immediate responses, when for example submitting interrupts via keyboard inputs. There is very little CPU idle time, duplication of software etc, but it is less reliable, there might be lower security and integrity, and potentially bad data communication. An example would be a chat messaging client or system.