Terminology

Because JavaScript was traditionally interpreted at runtime, and because runtimes in other languages (such as C#, mentioned before) do actually execute the code, many people incorrectly call the JavaScript engine the JavaScript runtime.

But, they are different things—the engine is the software that translates the high-level JavaScript code into machine-executable code, and then executes it. The JavaScript engine then exposes all the objects obtained from parsing the code to the JavaScript runtime environment, which can then use it.

So, JavaScript in the browser and Node.js both use the same V8 engine, but run in different runtime environments. For example, the browser runtime environment provides the window global object, which is not available in the Node.js runtime. Conversely, the browser runtime lacks the require global, and cannot act on system resources such as file systems.