what do I research?

I need to know what is happening when extra bits of information are passed around through method titles in xcode ie:

- (CGPDFPageRef)pdfPage:(NSInteger)index {

and

- (void)configurePageP:(ISVportrate *)page forIndex:(NSUInteger)index{
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when this happens it is a little annoying that I don't know whats going on or feel comfortable passing messages this way my self.

for example my app is made from some code chunks stuck together in a voodoo manner, one part of my app passes a message to a class this way... but the class only declares NSInteger index but never uses it:

@interface ImageScrollView : UIScrollView <UIScrollViewDelegate> {
    NSUInteger     index;
}
@property (assign) NSUInteger index;
@end

@implementation ImageScrollView
@synthesize index;
@end

I would really like to research this, can someone please point me in the right direction.

Thanks

---

It's just passing arguments with the message, similar to how printf("Hello\n") passes "Hello\n" to the printf function.

Apple's free The Objective-C Programming Language explains this very well, in addition to many other concepts that are important for you to feel confident in understanding Objective-C code. The first chapter after the introduction is actually on this very topic.