Middleware is the software that connects software components or enterprise applications. Middleware is the software layer that lies between the operating system and the applications on each side of a distributed computer network.Typically, it supports complex, distributed business software applications.n this more specific sense middleware can be described as the dash in client-server, or the-to-in peer-to-peer. ObjectWeb defines middleware as: The software layer that lies between the operating system and applications on each side of a distributed computing system in a network..