primitive root

A primitive root for a prime $p$ is one whose powers generate all the non-zero integers modulo $p$.
For example, 3 is a primitive root modulo 7 since:
3 = 31 , 2 = 32 mod 7, 6 = 33 mod 7, 4 = 34 mod 7, 5 = 35 mod 7, 1 = 36 mod 7.