Preemption in computing is refered to interuption of 
currently executed task by computer system or scheduler 
without application's cooperation in order to be resumed 
later. This process is known as context switching, when 
equal time slices are assigned by pre-emptive scheduler

Pre emption is releasing the process in order to serve 
another process to utilize the same resource. Context 
switching is the transfer of resource from once process to 
another process.

Preemption is when a task can be temporarily Interrupted &
expected to resumed later
Context switching is used for multi-tasking and Stores &
restores the CPU state.