Middleware is a software layer that sits between the operating system and the applications running on it. It is sometimes referred to as a “software glue” which connects different applications. The primary purpose of the Middleware is to provide an infrastructure consisting of core services like concurrency, transactions, threading, messaging, and security so that organizations can build business applications on top of it. Common Middleware examples include database middleware, application server middleware, message-oriented middleware, and web middleware.
As a hidden software layer that comes with a custom-built functional set of APIs, Middleware helps make communication and data management between the operating systems, databases, network services etc easier.