A select list (also known as drop-down list) is a form element that allows the user to select an option from a range of options.

Example: 

Usage:

Go to Components → Contact Enhanced → Form Fields, click on the New button, then set the Form Field Type to Select List.

Edit Custom Field Value by adding a new row for each new option. The first option is the field's value and the second is the label. 

Start the value with -- (two dashes) in order to create group field.

Select List options 

Select List Parameters

First Option
Automatically adds a first option with the -- Please select one -- label
First Option text
(Optional) The text to replace the first option default text
Show "other"
When enabled it replaces the Select list with a text field when the last option is selected
Show Datalist
Displays a list based on the select list options in case the user changes his mind and wants to use one of the options from the select list