General/VarArg refers to the capacity in a method or function for it to take a variable number of arguments above a fixed minimum. You declare a function with a variable number of arguments (var args) like this:
void myFunc(int a, ...);
and a vararg method like this:
-(void)myMethod:(int)a, ...;
The ellipsis is three periods in a row, and is how the compiler knows that this function/method can take more arguments after the explicitly specified ones.
An example of a vararg function is General/NSLog, which lets you pass a variable number of arguments after the initial General/NSString.
See also: General/UsingVariableNumbersOfArguments, General/VarArgsInObjCMethods, General/VariableLengthArgumentLists.