API (Application Programming Interface) is a modern way to communicate between two applications.
In another word, it can be termed as building block of modern day dynamic applications which deals with data transfer between the applications.
Two most popular API's are REST and SOAP which works on different protocols with the different set of rules.
There are several technologies(PHP, NodeJS, Python, Laravel etc) in which these API's can be developed.
These API's can be written for different purposes like mobile application development, payment integration, logistics, custom API etc.
