Official TWRP App is the official app developed by Team Win, that lets you make sure you stay up to date with the new versions of your personalized ROM. In order to install it directly from the app, however, you need to have root privileges.
The app is pretty simple to use thanks to its clean interface but it's not recommended to 'play around' with it if you're not exactly sure what you're doing , since you could seriously harm your device. At any rate, the app tells you this itself the first time you open it.
Official TWRP App makes it significantly easier to install a recovery on your Android. You just have to search for your device on the list, download it, and install it. The whole process takes only a few minutes to complete.