The new layout aims to make it easier to navigate to your favorite elements, with tabs along the top of the screen, and a more compressed view.
Each tab will take you to a dedicated experience centered around that aspect - like groups:
As per Facebook, the intention is to bring the desktop version more in line with the mobile app, while also making it easier for users to switch between usage areas.
"This redesign makes it easy for people to go from public spaces to more private ones, like Groups. There are tens of millions of active groups on Facebook, and when people find the right one, it often becomes the most meaningful part of how they use Facebook. That’s why we’re introducing new tools that will make it easier for you to discover and engage with groups of people who share your interests."
Given the rising use of more private spaces, it makes sense for Facebook to give them more dedicated focus, and to more clearly separate each, which may help boost engagement.
The refresh also reduces the presence of the iconic Facebook blue color scheme, which could also be part of an effort to shift perception, leaving the more recent scandals behind and starting anew.
As noted, several users are now seeing the new format - if you don't have it yet, it'll likely be coming soon.