The Verge 9318Ex-WE Expander has the following key features:

• 4.3" 480x272 pixel color backlit LCD display
• 18 programmable softkeys with LEDs
• Can be daisy chained with additional 9318EX-WE modules for a combined total of up to 3 expansion modules.
  In WebAdmin, expansion modules are sequentially identified, with the first module listed as 9318Ex1-WE, the second as 9318Ex2-WE and the third as 9318Ex3-WE.

For more information, see here.

You can use the Verge 9318-EX Expander for the same features as you would the line keys on your phone. See Program Memory Keys on Verge WE Phones for a list of available options.