An API or an Application Programmable Interface is used to establish a connection between two pieces of software. It is an interface that supports a direct built-in integration between a custom application, take an e-catalog for example, and a product information database.

The e-catalog and the database may be two separate applications, but the catalog can derive information and specific data from the database using an API. APIs currently exist almost everywhere around us.

If you perform a google search for the weather, you will see fairly descriptive details on google's weather page, but this does not mean that Google conducted these measures themselves. In fact, using an API, Google obtains these weather statistics from 'Weather.com' which is an independent entity. Similarly, APIs facilitate collaboration and allow for improved forms of SaaS.

Before we start looking at applications and integrations of APIs, it is important to understand the different types of APIs and API protocols that are relevant to our application: