W3C is an international community that develops open standards for the Web. They make sure that everyone follows the same guidelines and doesn’t have to support dozens of completely different environments.
A modern browser is quite a complicated piece of software with a codebase of tens of millions of lines of code. So it’s split into a lot of modules responsible for different logic.
Blink is a rendering engine that is responsible for the whole rendering pipeline including DOM trees, styles, events, and V8 integration. It parses the DOM tree, resolves styles, and determines the visual geometry of all the elements.
While continually monitoring dynamic changes via animation frames, Blink paints the content on your screen. The JS engine is a big part of the browser – but we haven’t gotten into those details yet.