The Honor 6X and bunch of other smartphones have gained TWRP support recently, expanding what seems like the ever growing list of mobile devices that will be able to install the custom recovery software so they can do a multitude of other things. Custom recovery software is important if you want to move into things like rooting your device and flashing custom firmware, typically referred to as ROMs, and TWRP has become one of if not the most popular solution for custom recovery options on devices, and this is likely due to their continued support for new devices and existing devices which they already offer recovery options for.
While the Honor 6X is one of the newest devices to receive support, it is far from being the only recent device which can now look to TWRP for custom recovery needs. Alongside the Honor 6X is actually a fairly large list of other smartphones, including the Wileyfox 2X, the Xiaomi Mi 5s Plus, the LG Spirit LTE, the LG K10, the Nubia ZTE Z9 Max, and tablets like the Galaxy Tab S2 8.0 and 9.7 Wi-Fi only models, as well as the Lenovo Tab 3 Plus in both Wi-Fi and LTE versions.
If you have one of the newly supported devices or if you have a device that's been on the support list for a while but have just decided to give TWRP a try, you can get the process started of installing it with a couple of different methods. The first and probably the easiest is with the TWRP app, although it's only the easiest in that once you're ready to flash the custom recovery the app does most of the work. To get to this point though to where the app is compatible, your device has to be rooted. If you aren't comfortable with rooting your device before you get the custom recovery installed, then the other method is to flash the TWRP image manually and go from there. If you're still not sure why you might need TWRP on your device, then it might be best to stay away from it, but if you're planning on rooting and flashing a ROM at some point, or changing between ROMs frequently, you want custom recovery.