What are the two types of combo boxes?
In simple and drop-down combo boxes, the user can type in the selection field instead of selecting a list item.
When should a list box be used instead of a combo box?
Generally, a combo box is appropriate when there is a list of suggested choices, and a list box is appropriate when you want to limit input to what is on the list. A combo box contains a text box field, so choices not on the list can be typed in.