Google has made several changes to the how Google search works document within its help center. The changes include how Google crawls both desktop and mobile, it has a new section on JavaScript, it talks about your CSS, scripts and image files and has a new section on what is a document - plus more.
I believe this was first noticed in the Local Search Forums but here are screen shots on what has changed.
You too can compare the live document to what is on archive.org. Here is what was changed that I noticed:
This section added details on rendering and how Google sees the page and the text on your page. It also talks about using the mobile-friendly testing tool. How and when to submit URLs to Google and more.
Then, if you expand the long version of the page, you see more changes.
Google made some tweaks to the hreflang line. Google also discussed images, CSS files and scripts again. Google also mentioned using the URL inspection tool and how you can test your pages with it.
This next small section was removed:
But this new section was added:
This section talks about JavaScript SEO and also discusses the primary crawl and secondary crawl.
Finally, Google added a whole section on "what is a document."
Again, if you want to compare yourself, see live document compared to what is on archive.org.
Forum discussion at Local Search Forums.