DropDown control looks by default like on the picture below. It allows user to select one value from the list. It can be either editable or not. In editable mode user also can type value he wants and which is allowed to be not one from the list. In non-editable mode, user can only select a value from the list. If you want to create a control with same behaviour and capabilities but with different type of items, you can start from CCustomDropDown class.

DropDown/ComboBox control(widget)