When making requests to APIs or other external resources, the response can take some time to return. In order to handle these asynchronous operations in a clean and organized way, JavaScript provides a concept known as promises.

Promises allow us to structure our code so that we can work with the response data once it has been returned, rather than having to wait for the response to arrive before continuing. This makes our code much more efficient and easier to read.

In a React application, we typically use promises when making requests to an API in a component. This involves creating a function that sends the request, returning a promise that resolves with the response data once it is received. We can then use this promise to update the component's state with the response data, rendering the content on the page.

The basic syntax for working with promises involves creating a new Promise object, which takes in a function with two arguments: resolve and reject. The resolve argument is called when the asynchronous operation is successful, and returns the data. The reject argument is called when the operation fails, and returns the error message.

Once we have created a promise, we can then use the ".then()" method to handle the resolved data, and the ".catch()" method to handle any errors that may occur.

Overall, the use of promises is a key feature of modern JavaScript programming, and is an essential skill to have when building React applications that rely on data from external sources.