REST has become one of the most important technologies for stateless communications between devices. Due to the lightweight and stateless nature of the REST-based services, its importance is likely to continue to grow as more devices are connected to the internet.

REST is an architecture style for designing networked applications. The idea behind REST is that, instead of using complex mechanisms, such as SOAP or CORBA to communicate between devices, we use simple HTTP requests for the communication. While, in theory, REST is not dependent on internet protocols, it is almost always implemented using them. Therefore, when we are accessing REST services, we are almost always interacting with web servers in the same way that our web browsers interact with these servers.

REST web services use the HTTP POST, GET, PUT, or DELETE methods. If we think about a standard Create, Read, Update, Delete (CRUD) application, we would use a POST request to create or update data, a GET request to read data, and a DELETE request to delete data.

When we type a URL into our browser's address bar and hit Enter, we are generally making a GET request to the server and asking it to send us the web page associated with that URL. When we fill out a web form and click the Submit button, we are generally making a POST request to the server. We then include the parameters from the web form in the body of our POST request.

Now, let's look at how to make an HTTP GET request using Apple's networking API.