The term is most commonly used for software that enables communication and management of data in distributed applications. In this more specific sense middleware can be described as the dash in client-server, or the -to- in peer-to-peer.
Middleware is computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue".Middleware makes it easier for software developers to perform communication and input/output, so they can focus on the specific purpose of their application.
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.
Middleware includes Web servers, application servers, content management systems, and similar tools that support application development and delivery. It is especially integral to information technology based on Extensible Markup Language (XML), Simple Object Access Protocol (SOAP), Web services, SOA, Web 2.0 infrastructure, and Lightweight Directory Access Protocol (LDAP)