After you confirm your email during registration you will be directed to a screen to create your username. This username will also serve as your NOAH lightning address.
For example, if you choose your username to be SatStacker then your lightning address will be firstname.lastname@example.org
Lightning addresses are used to send and receive bitcoin on the lightning network (Bitcoin's 2nd layer). This means you can completely avoid Bitcoin's long settlement times and fees - sending/receiving bitcoin "lightning" fast and almost completely free.
Register your lightning address today by registering at app.noah.com
You can learn more about lightning addresses here!