Restful Services provide uniform, standardized access with clear request requirements and response structure.

This means that Restful services allow us to know which data they will receive so that the server is able to handle this data, and that they provide a clear and standardized response, which can be handled by different applications accessing the service, like for an Example an App or a smartphone.

Lets take an Example to understand it in better way.

Have you ever think that Google map, Facebook, twitter, etc runs on almost every devices. Then the Question is How, are they developing their applications or services for each and every devices.

The Answer is NO.

Now as you are probably also aware, all these services live from the data they store on the internet or they can fetch from servers, so the solution certainly is a device. Instead, what is used here is a RESTful API, or some sort of API to which the different devices, or applications running on those devices, can reach out in order to fetch data, or store data, or do whatever they have to do. This underlines the importance of such APIs.