How do new properties appear in the browser?

Question

Browsers

Perhaps a stupid question, but I still don’t fully understand the process of the appearance of new properties. Let's say we have a flexbox property. Now it is well supported, but for example in 2011 it was different. It turns out that this property appeared due to the fact that new browsers began to appear, in which this property was gradually introduced? Is there any way to implement the flexbox property in an old browser?

Answer 1

There are guys who develop the standard. They make drafts of new features, then test them, collect feedback and promote the idea of ​​their implementation in different engines. And browser developers are racing to implement this so that their browser is the most modern ....
https://www.w3.org/TR/html51/