Level 3 is recommended for more than $50,000 USD worth of Bitcoin. It is a 3 of 7 HD Multisig setup where private keys are never on an Internet connected device.
Level 2 is recommended for storing between $5,000 and $50,000 USD worth of Bitcoin. It is a 3 of 7 HD Multisig setup that requires only a single laptop.
Level 1 is recommended for storing under $5,000 USD worth of Bitcoin. It is very easy to backup and restore and requires only a single computer to setup.
For more information and the source code click here for the GitHub Repo.
For the README click here