Middleware sits between operating systems and applications to simplify development of applications that leverage services from other programs. It provides messaging services so applications can communicate using frameworks like SOAP, REST, and JSON. Middleware connects disparate applications through services for concurrency, transactions, threading, and messaging, with more advanced implementations in integration platforms that add governance and risk management.

1. Middleware often sits between the operating system and applications on different servers and
simplifies the development of applications that leverage services from other applications. This
allows programmers to create business applications without having to custom craft integrations
for each new application.
Typically, middleware programs provide messaging services so that different applications can
communicate using messaging frameworks like Simple Object Access Protocol (SOAP), Web
services, Representational State Transfer (REST) and JavaScript Object Notation (JSON). The
systematic tying together of disparate applications, often through the use of middleware, is known
as enterprise application integration (EAI).
At a basic level, middleware provides services required to connect applications together such as
concurrency, transaction management, threading and messaging. More sophisticated
implementations of middleware principles are baked into modern integration infrastructure such
as enterprise service bus (ESB) and API management software to provide greater governance,
risk management and accountability.