What is parallelism and concurrency, and how to explain the difference to a non-technical person?

Parallelism and concurrency are two ways to perform multiple tasks simultaneously, but with different approaches.

• Parallelism is when tasks are actually executed at the same time, for example, on multiple CPU cores. Imagine you have several chefs, and each is preparing their dish at the same time.

• Concurrency is when tasks can start, pause, and resume to appear as if they are running simultaneously, but in reality, the processor switches between them very quickly. It's like one chef who quickly switches between different dishes, doing a little of each.

For non-technical people:

Parallelism is like several people doing work at the same time. Concurrency is like one person quickly switching between multiple tasks so that everything progresses.

In programming, parallelism requires multiple cores or threads, while concurrency can be implemented on a single core using a task scheduler.