What does this guide install?
This guide has the end goal of taking a completely unmodified 3DS from stock firmware to arm9loaderhax powered Custom Firmware. On some versions, it utilizes homebrew as a jumping off point, but Custom Firmware is still the goal.
Arm9loaderhax is the newest and best method of launching Custom Firmware that gives us nearly full control of the system only milliseconds into boot, which is similar to the effect of BootMii for the Wii.
The benefits of arm9loaderhax over other Custom Firmware launch methods are numerous, and as such it is recommended to use this guide over any other that relies on outdated software (such as menuhax or rxTools).