What STRLEN does

Here is a program that uses a function called “length”. Can you figure out what it does?

#include <cs50.h>
#include <stdio.h>
int length(string s);
int main(void)
{
  string name = GetString();
  int l = length(name);
  printf("The length of %s is %i\n", name, l);
}
int length(string s)
{
  int n = 0;
  while (s[n] != '\0')
  {
    n++;
  }
  return n;
}