"" is an empty string (I wouldn't call it an empty space - but I get your meaning).
An empty string can be found everywhere that isn't a string. That is, a string that doesn't contain anything. This is probably true of many languages.
This means there is an empty string before h, after h, before e, and so on.
Think about it this way, we know that
"" == ""
Empty string equals empty string. A return of
-1 would mean a failure; i.e. a non-match.
Note that the
"" isn't just at the beginning as some of the answers here would suggest. I.e. The string isn't just
"" + "hello".
Have a look at this:
string = "hello"