Answer
The natural log function has $(0, \infty)$ as its domain and $(-\infty, \infty)$ as its range. It monotonically increases over its domain and is continuous at each point. It is a bijective function on this domain and range. It has some very interesting properties the basic ones of which are:
$ln(a\times b) = ln(a)+ln(b)$ and $ln(a/b) = ln(a) - ln(b)$
Note that $ln(1) = ln(a/a) = ln(a)-ln(a) =0$
Work Step by Step
What it means is that ln(x) is a function that accepts real numbers from 0 to $\infty $ as inputs and outputs a real number. Being bijective means that each input gives only one output and that each value of output has only one corresponding input.
