A column view—technically referred to as a browser—lets the user view and navigate a data hierarchy using a series of vertical columns. Each column represents one level of the hierarchy and contains horizontal rows of data items. Within a column, any parent item that contains nested child items is marked with a triangle icon. When the user selects a parent, the next column displays its children. The user can continue navigating in this way until they reach an item with no children. The user can also navigate back up the hierarchy in order to explore other branches of data.
Consider using a column view when your data doesn’t need to be sorted multiple ways, or when you have a deep data hierarchy in which users tend to navigate back and forth frequently between levels. The Finder offers a column view (in addition to list, icon, and Cover Flow views) for navigating directory structures.
Show the root level of your data hierarchy in the first column. Users know they can quickly scroll back to the first column to begin navigating the hierarchy from the top again.
Consider showing information about the selected item when there are no nested items to display. The Finder, for example, shows a preview of the selected item and information like the creation date, modification date, file type, and size.
In general, let people resize columns. This is especially important if the names of some data items are too long to fit within the default column width.