What is an API?

Answer

APIs are toolboxes that developers give to each other to make it so that each application can work between one another. 

For example, in a data cleanup application we wrote we needed to validate the physical addresses that we had. We used an API provided by another vendor that validated the address by sending the original address in a specified format and getting a message back in a specified format. 

Common APIs we work with come from Microsoft Dynamics, Salesforce, CiviCRM, SmartyStreets, Google Maps, and many more.