This is the best summary I could come up with:

This will split ChromeOS's Linux OS from the Chrome browser, allowing Google to update each one independently.

Google documentation on the project says, "On Chrome OS, the system UI (ash window manager, login screen, etc.)

Lacros separates this functionality into two binaries, henceforth known as ash-chrome (system UI) and lacros-chrome (web browser)."

Part of the project involves sprucing up the ChromeOS OS, and Google's docs say, "Lacros can be imagined as 'Linux chrome with more Wayland support.'"

Users probably won't notice anything, but the feature should make it easier to update Chrome OS and might even extend the lifetime of old ChromeOS devices.

I'm a bot and I'm open source!

(I) don't trust Google

Right in the linuxy

The weird name Lacros means Linux And ChRome OS.

*Linux-y again - it's Gentoo based after all.