Introduction - If you have any usage issues, please Google them yourself
P is a prime number based, a is the primitive root p, that is, a1, a2, a3, ..., ap-1 in the mod p under 1 to p-1 for all values, so for any b belongs to (1, ..., p-1), there are only i belong to (1, ..., p-1) makes ai mod p equivalent to p. Said i was under the modulus p to a for b at the end of the discrete logarithm.