The Google Play team has been working on retooling the "My Apps" UI within the Play Store for quite some time now, and it has gone through quite a few changes already. And the latest update that a handful of users are seeing, adds a few more tabs to the mix, as well as sorting results. These changes are only available for some, as Google appears to be A/B testing it right now.
Starting off with the new tabs. There are now three tabs, at least in this iteration. There are Updates, Installed and Library. These are all pretty self-explanatory. With Updates being for apps and games that are in need of an update, of course the Installed section is everything installed on that device (so if you have multiple devices, this list could look different on each one), and then Library is full of all the apps and games that you have ever downloaded. These are much more helpful compared to the Installed, All and Beta tabs that are currently in the Google Play Store.
Now the other change is the sorting in the Installed tab. It appears that users will be able to sort apps and games alphabetically, by size, by last update time and by last time used. Some pretty useful sorting options there for the Google Play Store, and should make it easier for users to see what all is installed on that device, as well as how often they use a certain app (and perhaps uninstall it if they aren't using it that often and then save some space on their smartphone).
Currently, it's unclear how long Google will continue to test this, but it does appear that they are still working on this and innovating the interface. Google may continue to test this new interface for months and months, or they may roll it out to everyone next week. With Google, it's really tough to say, and this doesn't appear to be available to everyone, so there's no real way to force the new UI to work on your smartphone, tablet or another device that accesses the Google Play Store.