neowin[.]net/news/the-windows-10-may-2021-update-is-now-available/
microsoft[.]com/en-us/software-download/windows10
For most people what this means is that if/when you click the Check for Updates button, now you know what the update that *may* show up is all about.
And you have a new ISO to use if/when you install Win10, or reinstall Win10 when something breaks -- went that route both with an Insider copy & with one of my tablets when Windows Update broke, and no updates would successfully install. FWIW I've had it with all the *supposed to fix Windows Update* stuff, & now just save time reinstalling -- I mount the ISO, if necessary, like with my tablet, I'll copy the files to a USB stick, then run setup.exe, keeping all my files and apps etc.
At any rate, this is the smallest version update ever in terms of stuff that's new -- seems like Microsoft felt they had to release something, so this is it. They've canceled Windows 10X, so now to help justify all the work they put in trying to make Win10X happen, they're migrating as many of the new features and designs into regular Win10 as they can manage by this fall's version update/upgrade.
And, in what seems the norm nowadays, no telling when the update to 21H1 will show up for you. Like the new Taskbar News & Weather Widget, it'll show up when it shows up. If anyone's cracked how Microsoft decides who gets offered the update & who doesn't, it's not been widely published AFAIK.
