The W3C was the original standardization organization for the web.
They wanted to create standards that allow easy implementation by others, and were willing to make some tradeoffs with backwards compatibility for that (see XHTML).
The browser vendors obviously oppose this, and want standards that just formalize what they already implement. As result, the browser vendors created their own standards committee, which standardizes whatever the browsers already do (if existing). This is the WHATWG.
As result, the web standards situation has gone to insanity. The WHATWG URL spec contains 4 pages of pseudocode and algorithm definitions for how Chrome parses URLs, and how you should as well, and the W3C, still being relied on by the other actors on the web that aren’t the 4 largest browsers, has to copy the WHATWG spec as base for their own specs, because browsers will ignore whatever the W3C says anyway.
But remember that the WHATWG proposed to the W3C that the W3C should copy the WHATWG specs as base for their own specs: https://en.wikipedia.org/wiki/WHATWG#cite_note-9
They wanted to create standards that allow easy implementation by others, and were willing to make some tradeoffs with backwards compatibility for that (see XHTML).
The browser vendors obviously oppose this, and want standards that just formalize what they already implement. As result, the browser vendors created their own standards committee, which standardizes whatever the browsers already do (if existing). This is the WHATWG.
As result, the web standards situation has gone to insanity. The WHATWG URL spec contains 4 pages of pseudocode and algorithm definitions for how Chrome parses URLs, and how you should as well, and the W3C, still being relied on by the other actors on the web that aren’t the 4 largest browsers, has to copy the WHATWG spec as base for their own specs, because browsers will ignore whatever the W3C says anyway.
But remember that the WHATWG proposed to the W3C that the W3C should copy the WHATWG specs as base for their own specs: https://en.wikipedia.org/wiki/WHATWG#cite_note-9