The actual, correct answer is that Q factor is a * m e a s u r e o f t h e d i s t a n c e b e t w e e n t h e p e d a l s * . A wider hub will tend to have a higher Q-factor. Some cranks angle outwards, which also increases Q-factor.
Most people prefer lower Q-factor (pedals closer together), but others like their legs more splayed out. In practice, it generally doesn't matter much.