It's mostly a historical term of art: Browser plugins refers to NSAPI plugins (and could also refer to OLE/ActiveX plugins), which is older and now obsolete, and is based on plugging native code in compiled binary dynamic libraries into the existing browser app (or OLE control container), without necessarily requiting an extension language like JavaScript / Visual Basic.
Browser extensions refer to more recent JavaScript centric extension techniques (like the older Firefox XUL extensions, and more modern Chrome/etc extensions), using JavaScript as a browser extension language, throwing in some XML and CSS, and coding most if not all of the plugin in JavaScript, instead of linking compiled binary code.
Python makes a distinction between "embedding" and "extending", that doesn't map directly into the browser plugin/extension dichotomy, but is kind of similar -- it's a question of "who's on top", and embedding usually implies some extending:
Extending Python means building modules that Python code can import to access the features the modules supply. Embedding Python means executing Python code from an application coded in another language. For such execution to be useful, Python code must in turn be able to access some of your application’s functionality. In practice, therefore, embedding implies some extending, as well as a few embedding-specific operations. [...]
>This document describes how to write modules in C or C++ to extend the Python interpreter with new modules. Those modules can not only define new functions but also new object types and their methods. The document also describes how to embed the Python interpreter in another application, for use as an extension language. Finally, it shows how to compile and link extension modules so that they can be loaded dynamically (at run time) into the interpreter, if the underlying operating system supports this feature.
Browser extensions refer to more recent JavaScript centric extension techniques (like the older Firefox XUL extensions, and more modern Chrome/etc extensions), using JavaScript as a browser extension language, throwing in some XML and CSS, and coding most if not all of the plugin in JavaScript, instead of linking compiled binary code.
Python makes a distinction between "embedding" and "extending", that doesn't map directly into the browser plugin/extension dichotomy, but is kind of similar -- it's a question of "who's on top", and embedding usually implies some extending:
https://www.oreilly.com/library/view/python-in-a/97814919138...
Extending Python means building modules that Python code can import to access the features the modules supply. Embedding Python means executing Python code from an application coded in another language. For such execution to be useful, Python code must in turn be able to access some of your application’s functionality. In practice, therefore, embedding implies some extending, as well as a few embedding-specific operations. [...]
https://docs.python.org/3/extending/index.html
>This document describes how to write modules in C or C++ to extend the Python interpreter with new modules. Those modules can not only define new functions but also new object types and their methods. The document also describes how to embed the Python interpreter in another application, for use as an extension language. Finally, it shows how to compile and link extension modules so that they can be loaded dynamically (at run time) into the interpreter, if the underlying operating system supports this feature.