Application Programming Interface (API) was first introduced by Salesforce.com on February 7th 2000. In the simplest terms, APIs are sets of requirements that govern how one application can talk to another. APIs are what make it possible to move information between programs. An API is a software-to-software interface, not a user interface. With APIs, applications talk to each other without any user knowledge or intervention and provide developers with standard commands for performing common operations so they do not have to write the code from scratch. Plug-and-play enables a better customer experience.