Since its been bumped, I know YC already pointed this out but perhaps not clearly enough - this is not the meaning of Syntax. This is useful information to be sure, beecake. Thanks. But to anyone that is interested in programming - Syntax is as YC put it, the rules of the language. What you describe here is what is known as 'Parameters'.
For example, AngelScript is based on the C++ 'syntax', meaning its use of certain keywords (like variable declarations int, float, string or function declarations like void, int, string etc), the way you assign or compare values (like '=', '==', '&&' etc) or the way you type strings (e.g. badstring, "goodstring") are very similar if not in most cases, the same.
In contrast, parameters are where you have things like
void Function(string &in ThisIsAParameter)
The reason it is referred to as the 'callback syntax' on the wiki is because typing in the correct parameters (like 'void Timer(string &in asTimer)') is a syntax issue - get it wrong and you have used the incorrect syntax because you wrote the parameters wrong, like 'void Timer(int asTimer)'.
Another example of a syntax issue related to this would be AddTimer(ThisStringDoesntHaveQuotationMarks!, 1, "ThisStringIsMissingAQuotationMark!);
because you did not write the language correctly, its like a spelling/grammer mistake, you need " surrounding a string
For anyone who frankly doesn't give a crap about programming except as much as they need to script their maps, please disregard all of the above and enjoy the information beecake has very kindly provided
(note: correct use of smiley conforms to beecake's forum syntax, as set out above)