What Is Logarithm?
A logarithm answers the question "what exponent do I need?" Specifically, log base b of x is the exponent you'd raise b to in order to get x. Logarithms are the inverse operation of exponentiation, the same way subtraction is the inverse of addition. Base 10 (common log) and base e (natural log) are the two most widely used.
Example
log₂(8) = 3, because 2³ = 8. In other words, you need to raise 2 to the 3rd power to get 8.