What does API mean again?

Answer 1

You can think of this as a way of communication with an application (yours or external) for you to request a service it can provide you with.
Take a look at my GeoProject code to see how I request some geolocation data from Google geocoding API:

https://code.sololearn.com/c57gr6Ay31s9/?ref=app

Answer 2

An application programming interface (API) is a particular set of rules ('code') and specifications that software programs can follow to communicate with each other. It serves as an interface between different software programs and facilitates their interaction, similar to the way the user interface facilitates interaction between humans and computers.

How is it used?

The same way any set of rules are used.

When and where is it used?

Depends upon realm and API, naturally. Consider these:

The x86 (IA-32) Instruction Set (very useful ;-)
A BIOS interrupt call
OpenGL which is often exposed as a C library
Core Windows system calls: WinAPI
The Classes and Methods in Ruby's core library
The Document Object Model exposed by browsers to JavaScript
Web services, such as those provided by Facebook's Graph API
An implementation of a protocol such as JNI in Java

Happy coding.

Credits:- Stack Overflow

Answer 3

an interface is defined that allows other code to interact with another set of code to perform predefined sets of instructions. an example would be DOM interaction in js that is provided by the browser.

Answer 4

application programming interface

Answer 5

I'm sorry, I understand what it stands for just not what it really means