Asynchronous versus parallel versus concurrent programming

Asynchronous programming involves some calculations time-intensive tasks, which on the one hand are engaging a thread in the background but do not affect the normal flow of the program.

Parallel programming incorporates several threads to perform a task faster and so does concurrent programming. But there's a subtle difference between these two. The program flow in parallel programming is deterministic whereas in concurrent programming it's not. For example, a scenario where you send multiple requests to perform and return responses regardless of response order is said to be concurrent programming. But where you break down your task into multiple sub-tasks to achieve parallelism can be defined as the core idea of parallel programming.