Essentially means you passed stage one. But before you get to stage 2 you have to complete the personality questionnaire. And I believe it is pass/fail.
Its all questions about yourself and personality, can't really be revised for, just a case of doing it. Oh, and don't try and second guess it, answer it honestly, they can apparently tell when you are trying to give the answers you think they want. From memory, it was one of the most boring and least entertaining 40 minutes of my life.
More details in the sticky "NATS Recruitment" thread at the top of this board.