* ✨ Add illustrations for Concurrent burgers and Parallel burgers. PR [#5277](https://github.com/tiangolo/fastapi/pull/5277) by [@tiangolo](https://github.com/tiangolo). Updated docs at: [Concurrency and Burgers](https://fastapi.tiangolo.com/async/#concurrency-and-burgers).

### Translations

# OpenAPI Webhooks

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps