What is API's and why to use them ?

API stands for Application Programming Interface. It is a set of protocols, routines, and tools for building software applications. Essentially, an API allows different software applications to communicate with each other, share data, and perform actions.

There are many reasons why APIs are used. For example:

1. Integration: APIs allow different software applications to communicate with each other, which is crucial for integrating systems and sharing data.

2. Scalability: APIs can help developers to build scalable systems, by making it easier to break down functionality into separate components that can be independently scaled up or down.

3. Innovation: APIs can enable developers to build new applications and services on top of existing platforms and data sources, unlocking new opportunities for innovation.

4. Efficiency: APIs can help to automate repetitive tasks and reduce manual effort, improving efficiency and productivity.

Regarding Facebook API and Google API, these are examples of public APIs that provide access to the data and functionality of Facebook and Google services, respectively. Developers can use these APIs to build applications that integrate with Facebook and Google services, and take advantage of their data and functionality in their own applications. For example, a developer could use the Facebook API to build a social media monitoring tool, or use the Google Maps API to build a location-based service.