A citiy alias allow you to point a a city that someone searched for to a real city.

Example:

Alias: Big Apple
City: New York
State: NY
Country: United States

Using the following setting would allow a user to enger Big Apple in the city search and they would be sent to New York
and use for this feature would be Paris. You coulld enter the following

Alias: Pairs
City: Paris
State:
Country: France

This would list Paris France verses asking the user if they wanted Paris France or Paris Texas