Amway? LB? MLM or network marketing? Is it legal? Worth to join? What is it about?

Recently I hv heard more n more about Amway and LB, of course others company too... they usually invites us to join their class or talk.. talk about their plan..the benefits of joining... n also shows u the example of how they success (story sharing)... sounds n looks good.. but does it really work? realistics?