Microsoft is beginning to roll out the Windows 10 October 2020 update, formerly known as 20H2, with a bunch of changes to the UI including changes to the start menu and tablet mode, Alt + Tab in Edge and Xbox Game Pass.
The Start menu will be getting a design with transparent tiles, which should make them look better with your theme or wallpaper. The taskbar will also become more touch friendly, and will change automatically when you go into tablet mode, without asking whether that's what you want. Additionally, Microsoft is making some changes to notifications to better indicate which piece of software it's coming from.
Those with high refresh displays will be able to change the refresh rates in settings, under Settings > System > Display, Advanced display settings.
There are some new Edge features, which are exclusive to the browser on Windows 10. Alt + Tab will let you tab through open, well, tabs. Additionally, when you hover over a favicon, it will highlight all of the open tabs from that site.
As is typical for major OS updates, Microsoft will be throttling the release of this update. The May 2020 update took quite some time to reach some PCs and also had quite a few bugs, so this approach may be for the better. The company wrote that "In this work, learn and connect from home environment where people are relying on their PCs more than ever before, we are taking a measured seeker-based rollout approach to the October 2020 Update."
Devices with hardware compatibility issues may also trigger safeguards, so it may be a bit until the October 2020 update hits your laptop or desktop.
If you want to see if the October 2020 update is ready for you now, go to Settings > Update & Security > Windows Update and click on Check for updates. If you want to roll the dice and force update your PC to the latest build, you can use the Media Creation Tool (opens in new tab).