Any API lets you connect to a service you use that has a public API, to share its data.
A public API, or Open API, means the service can be accessed by customers' systems. BigBusiness includes a raft of tools to authenticate, connect, read, and write your data.
This is a starting point for a simple lookup, getting new data, or posting coded results. BigBusiness also has process-oriented connections like credit card, ecommerce, or tax.