There are comboboxes and listboxes.
Comboboxes can Drop down to show a list of the items available in the
combobox.
Comboboxes show ONE item at a time and when the drop down is not activated
show only the first "visible" column. They are good for entering data,
selecting one item from a list, etc. They generally take up only a small
amount of space.
Comboboxes also have the ability to use "type-ahead" functionality. As you
type into the combobox, the combobox automatically attempts to match what
you have typed to a matching item in its list.
Listboxes show multiple rows and multiple items at one time on the screen.
They are good for selecting item(s) and displaying many choices at one time.
Since they usually show more data at one time, they take up a larger amount
of screen space.