By definition, enterprise integration software is the field of enterprise (large company/business) software architecture that focuses on system interconnection, electronic data interchange, product data exchange, and distributed computing environments. The code that allows two systems to talk to one another is a connection, and as a company grows these connections multiply. Connections are often reusable between different groups and departments internal to the company, but many times, there is no way to advertise that the existing connection exists or share the documentation that enables the connection to operate. This leads to companies building messy point-to-point connections, making integration exponentially harder.
Enterprise integration software make integration less complex because they house all integration assets in a universally consumable manner. Softwares make upgrades easy and quick, have support systems, and make systems communicate seamlessly. Most importantly, enterprise integration software surface all the connections, both singular and redundant, into a cohesive layout or IDE (integrated development environment) and clean up the point-to-point disorganization by way of APIs.
An API is an application programming interface, or a fragment of a code that provides functionality or information.
To understand what an API is, think about driving a car. If the steering wheel rotates right, the car will turn right, and that is all that the driver needs to know in order to drive from point A to point B. She doesn’t need to know the underlying motor complexities in order to turn the car right.
An API is like the car’s steering wheel: it is the only point of communication between the driver (programmer) and engine and hides the code complexities that make the act of turning the car feasible.