The best thing about iPhone development is interface builder (IB) and his capabilities. Interface Builder is a great visual design tool you use to create the user interfaces of your iPhone application and Mac OS X applications. Using IB graphical environment you can assemble windows, views, controls, menus, and other elements from a library of configurable objects.
You can arrange these items how ever you want, set their attributes or make connections between them, and then save them in a special type of resource file called a nib file for Mac OS X and xib file for iPhone application (everyone in iphone development uses nib term).
For example, a typical iPhone application has only one window, which provides the backdrop for all of the application’s content. Applications can include additional windows, if desired, but doing that is rare and generally not recommended. Because it is an integral part of the application’s interface, you usually put your application’s main window in the main nib file so that it is loaded at launch time.
The main nib file typically comes preconfigured with a window object that you can simply modify. To add a window to your nib file manually, simply drag a window object from the library and either drop it onto the desktop or onto your Interface Builder document. Dropping a window object onto the desktop adds that window to the top level of the active IB document window.
In iPhone OS, windows do not have title bars or other visual elements that would require different window styles and IB automatically sets the size of each window to the size of the device’s screen. If your window is configured to display a status bar, IB displays a mock status bar to help you position your content. This status bar is not saved with your nib file.
When you double-click a window object, IB opens that window on the desktop. The content area of the window represents the design surface and is where you build the appearance of your window. There is bunch of stuff you can do with IB that reduces time and makes your development easier.