Level 0: Confirms user's identity with facebook authentication. It is the least level of verification.
Level 1: Let's say if person "Gautam" wants to get verified with Level 1. If person "Adithya" is already a member of GotCouch with 'Level 1' place, then he can verify "Gautam". Even then "Gautam" needs to get his address verified for proving his full identity.
Level 2: It is the maximum level of authentication one can get. If "Level 1" users visits another "Level 1" user's couch for more than ten times and recommend him to others, then that user will get "Level 2" Verification.
Though we care about your security and try to show you genuine users as much as possible, it is your own decision to allow them enter your home!