Synchronous programming is code executed on the spot, and the results being immediate. Asynchronous programming, by contrast, is not synchronous programming. This means code might be executed later, and results are not immediate.

One way to achieve this is by using multithreading, but it is not the only way. The ways in which async programming can be achieved are:

Multithreading

Callbacks

Tasks / Promises / Futures

async / await

Reactive programming