How does the engine and browser affect a particular specification?

Question

Browsers

There are many browsers, and there are engines. I heard that it is necessary to support not browsers but their engines, but it's not entirely clear how to check which engine supports which specification?
If you support only the engine, and not the browsers themselves, it turns out that if webkit supports some kind of w3c specification, then other browsers will automatically start supporting it, or not? (and here I don’t quite understand: How does the engine and browser affect some specification? )

Answer 1

There is w3c and whatwh - two offices that write specifications. The first ones think for a long time, and come up with something very cool for the future. Others are much faster to respond to innovations, here is the history of canvas, for example .
There is no such browser called webkit.
Webkit is one of the internal parts of the browser. If the webkit developers add some new feature, then all browsers that have this engine inside will receive this feature automatically as soon as they update, of course. And those browsers that have a different engine will have to add it in some other way.