Don't understand "&" after string

[HarryNewgas]

In creating this function, what does the &guessword part mean? Thanks

int letterFill (char guess, string secretword, string &guessword)

[Chervil]

It means the parameter guessword is passed by reference, rather than by value.

I take it you read part 1 of the tutorial. Now it's time for part 2
http://www.cplusplus.com/doc/tutorial/functions2/

[HarryNewgas]

Thanks, I'll try to understand it :D