What is javascript runtime?

Since question have been asked multiple times but I’m not able to understand it clearly.

As per answers provided, JavaScript runtime mean where our javascript code is executed.

Now definition of Nodejs, it is an asynchronous, javascript runtime, does it mean inside nodejs javascript is executed?

Also, javascript runtime environment, does it mean the environment or machine setup where javascript code are executed?

Sorry for repetition of question , but I would like to be definite whether my understanding is correct or not.

Answer

Whether it’s running inside a web browser or outside of it, the JavaScript source code that you write is first “compiled” to an internal format (a data structure), and that is then “run” by the language interpreter – this is the “runtime environment.” The programming that you write tells this interpreter what to do for you. All interpreted languages work in this way. With most languages there is more than one available implementation. Edwin’s comment above leads to a list of the various interpreters that have been created for JavaScript.