Can take resource away, use it for something else, then give it back later. Examples are file space, terminal, and maybe memory. This distinction is a little arbitrary, since anything is preemptible if it can be saved and restored. It generally measures the difficulty of preemption. Implication is that resources aren't easily preemptible.
Implication is that resource is preemptible.
That is, waiting for CPU time. Scheduler and dispatcher determine transitions between this and running state. Transitions into and out of this state are caused by various processes. The scheduler is a piece of OS code that decides the priorities of processes and how long each will run. Goals for Scheduling Disciplines Efficiency of resource utilization.