Internet Explorer, Mozilla Firefox and Opera are referred to as:

Internet Explorer, Mozilla Firefox and Opera are all web browsers, programs used to view pages on the web.

A browser requests pages from web servers and renders their HTML into readable content.

A web server is the machine and software that stores and delivers pages, not the tool that displays them.

System software like an operating system manages the hardware, while a browser is an application on top of it.

Application software is the broad class, but the precise name for these three programs is browsers.

Modern browsers add tabs, extensions and secure HTTPS handling to the basic page-viewing job.