Definition

Classes

There's a great Class explanation provided by Apple.

Instance Method

An instance method is a method on the instance of a class. For example, NSArray's count method is an instance method because it works on an instance of an NSArray object.

Instance Variables

This is useful for instance variables.

Self

self is a keyword used as a reference to an object executing a method. For example, in the Crystal Ball app, we see the following line of code:

self.predictionLabel.text;

This indicates that predictionLabel is a property of our THViewController class.

Objects

In Objective-C, objects are a big thing. They represent instances of a class. For example, in this line of code:

NSString *string = @"Hi Treehouse!";

I've created an instance of an object, of the class NSString, then setting it to the value "Hi Treehouse!". This is discussed in detail in Objective-C Basics.

Instance

This is a great explanation on instances.

Frames

Frames represent a rectangular area on the device's screen, and are fundamental in iOS programming.

Interface

The @interface is where you declare your properties, class and instance methods, among other things.

Implementation

Implementation is the actual implementation of the methods we've declared in our @interface.

These were all very rough explanations: however, Treehouse's iOS development track will teach these things in much greater detail. I suggest you start out with Objective-C Basics and test the waters to see if it's something you'd like :)

Thanks so much, by the way I have finished Objective-C basics so I was just reviewing my terms.