From Cisco help files:
Directory lookup rules transform caller identification numbers into numbers that can be looked up in the directory. Each rule specifies which numbers to transform based on the beginning digits and length of the number. For example, you can create a directory lookup rule that automatically removes the area code and 2 prefix digits from a 10-digit telephone, which would transform 4085551212 into 51212. If
Cisco Unified Communications Manager Attendant Console can match the number with a user in the speed-dial entries of the attendant or in the directory, the attendant console displays the name in the Call Detail window.
Application Dial Rules - The administrator uses dial rules configuration to add and sort the priority of dialing rules. Dial rules for applications such as Cisco Unified Communications Manager Assistant automatically strip numbers from or add numbers to telephone numbers that a user dials. For example, the dial rules automatically add the digit 9 in front of a 7-digit telephone number to provide access to an outside line.
For example, in Cisco Unified Communications Manager Assistant, the assistant can perform a directory search from the assistant console. The assistant can drag and drop the directory entry to the My Calls panel on the assistant console, which invokes a call to the number that is listed in the entry. The dial rules apply to the number that is listed in the entry before the call gets made.
