The web contains so much data to really drown in it. Most of these data are available via REST services. Just to access the plethora of data available via Google Services, it would be worth it to learn how to call a REST service.
In this section, we explain what a REST service is, how it operates, and the methods available to call them. Some services can be called just via a GET Request, some need a more complex POST Request, and some even more advanced REST access methods. Some services do not need authentication, some need simple authentication via an API key, and some have to go through the OAuth authorization protocol. It is all explained here.