gui design - What are the little arrows called that hide additional details?

In UI design, sometimes settings are hidden behind a little arrow or "+" symbol. When the user clicks on it, the item expands to show additional details.

Does this UI pattern have a name? Other than "little arrow"?

For example: "Click on the little arrow and edit the details for..."

Versus: "Click on the and edit...etc..."

Answer

The overarching design pattern itself is generally referred to as progressive disclosure. I personally often hear it referred to as a collapsible section/panel. Yahoo's pattern library lists a similar concept as Expand Transition, although that pattern speaks more to the transition from collapsed to expanded.

When speaking about the icons used in these type of expand/collapse implementations, I generally refer to them by their canonical name. For the plus symbol I would therefore say "click the plus icon to expand the content and/or show the details." For the arrow indicators I would use the name of the symbol yet again, as in "click the arrow to expand the content and/or show the details."