Updating foxfire plugins

What is the exact difference between plugins, add-on and extensions.

As you may or may not know, Chrome has dropped support for NPAPI plugins (as of version 45) and Firefox has done so as of version 52 (excluding the version 52 Extended Support Release, which will support them for another year).

Fire Breath 2.0 is now being used in production by several companies and can produce "plugins" (not really plugins, but work similarly) which can work with Google Chrome and Firefox via Native Messaging via a helper extension.

Also I have read the answer provided in firefox add-on vs. plugins and However I want to understand these differences especially in firebreath where plugins execute automatically through user's consent and add-on should install manually.

Also I think plugin embed in htm page while add-on is in form of a separated file like xpi in fire-fox.

Plugins have been responsible for a lot of security problems, since they actually run native code.

This has led to a lot of discrimination against them -- much of it deserved.What is your opinion about 4 definitions that I have mentioned in the question?Is it true that plugin embed in htm pages and have not any separated files like xpi?I repeatedly get a web page popping up in IE that says "Adobe Flash Player - Your Flash Player may be out of date" which triggers an IE pop up asking what I want to do with Flash The website is Is this really from Adobe and legitimate?The Native Messaging method relies on an Extension -- we did this primarily to confuse everyone, of course, but also because it was the only way to allow us to communicate with Fire Breath plugins from the page in Google Chrome or Firefox.