It means that not only the machines can fail by shutting down - they can send incorrect data. I recommend this: http://techtv.mit.edu/genres/19-engineering/vid

It means that not only the machines can fail by shutting down - they can send incorrect data. I recommend this: http://techtv.mit.edu/genres/19-engineering/videos/16444-practical-byzantine-fault-tolerance http://techtv.mit.edu/genres/19-engineering/videos/16444-pra... which helped me learn how it works ~6 years ago :)