While I study C,

When i study C(detailed part- rand function), i have a some question

first i write a code RAND function, i write

enter image description here but here is a some mistake. Actually, i wanna write ( rand()%n-1) but, my mistake, i write this code ( rand()&n-1)

but result is same.

why( & and % result) is same? so & and % is different mean, what means?