platform

A  platform  in the context of software/services is a collection of related APIs/protocols/formats that can be used to build sites/apps, and sometimes misleadingly used to refer to apps themselves, or suites of apps, to exaggerate their sense of importance, value, or impact.

OS Examples
Operating systems are platforms.
 * iOS
 * MacOS
 * Android

Not platforms
apps are not platforms. Sometimes suites of apps are called a "platform" to exaggerate their sense of importance or as a form of superlative marketing/consultant-speak, when really they're just tools. E.g. "Communication platforms and software can be indispensable".

Then again, sometimes it's just the best word to use under certain cicrumstances: Always Own Your Platform

Online meeting platforms
Online meeting "platforms" are not platforms, they are just a certain kind of app, or sometimes suites of apps that themselves often run on different platforms.

See:
 * chat