Context Switch
In plain terms
Saving one task's state to run another.
Going deeper
A context switch stores a process's or thread's state and loads another's so the CPU can switch tasks, enabling multitasking at a cost. Switching isn't free.
Under the hood
Saving/restoring registers and memory mappings adds overhead; excessive switching hurts performance.
Examples
Multitasking, thread switching, performance overhead, OS scheduling.
Think of it like...
Like bookmarking one book to pick up another, then back again.