The term was introduced to me when i was trying to deploy a django application to the server. Those who don’t know, django is a python web framework. While deploying we use nginx. It is a web server same as apache. WSGI comes in role between a server and a application. It stands for Web Server Gateway Interface and is a standard protocol used between web server and web application. It is not a server, a python module, a framework, an API or any kind of software. Both server and application interface sides are specified in the PEP 333( it specifies a proposed standard interface between web servers and Python web applications or frameworks, to promote web application portability across a variety of web servers).
The goal is to provide a relatively simple yet comprehensive interface capable of supporting all (or most) interactions between a Web server and a Web framework. An additional goal is to support “middleware” components for pre- and post-processing of requests: think gzip, recording, proxy, load-balancing.
Hope this information was beneficial :)