What is a logarithm?

Answer 1

log_a (b) [in words - log a of b], is like asking - what power of a equals b.

For example:

log_10 (100) = 2 because 10^2 = 100

log_2 (16) = 4 because 2^4 = 16

Answer 2

Logarithms are the INVERSE function of powers/exponentials.

a = b^(c)

Then its inverse is

log(b) a = c

As a number set /

10^3 = 1000

Then

log(10)1000 = 3