Hi @bridgecoder.

why does it work without using "func great"

In my code great is of type (String,String) -> String, which basically says this is a closure that expects two String values as parameter and returns another String value. And a closure is basically the same thing as a function.

and that $0 == $1 part too?

In a closure you can access the input parameters using $-Syntax, e.g. $0 is the first parameter, $1 the second, etc.
Hope that helps.