The List style is very similar the the UIPickerView in iOS, where you use the crown to select a sequential list of items. The items can be images and text, just text or just images.

The Stack Style animates the items like a stack of cards, providing an attractive way to select an item.

The Sequence Style replaces each image, allowing you to quickly flip between your choices, and also can be used to animate progress bars.

Focus Styles

For each style, you can indicate a focus style, which indicates how you want watchOS to display which picker is in focus. If there is only one picker on the screen, you may want to use None. If you have multiple pickers, you need to indicate which control is in focus and will be affected by the Digital Crown. For example, when customizing the clock face, Outline focus styles are used to indicate which complication is in focus to be adjusted by the Digital Crown.

Each picker item can be annotated by a caption, which can be used to indicate the group or secondary information about the item that will be displayed while picking. The caption can be useful if you are picking images, for example.