iOS Programming: The Big Nerd Ranch Guide, 7th Edition

Presentation Styles

When you present a standard view controller, it slides up to cover the window. This is the default presentation style. The presentation style determines the appearance of the view controller as well as how the user can interact with it. Here are some of the more common presentation styles that you will encounter:

.automatic	Presents the view controller using a style chosen by the system. Typically this results in a .formSheet presentation. This is the default presentation style.
.formSheet	Presents the view controller centered on top of the existing content.
.fullScreen	Presents the view controller over the entire application.
.overFullScreen	Similar to .fullScreen except ...