Expeditions is a mini-game in City of Wonder that you can play to win experience, silver or increase your population.
There are three kinds of expeditions:
It sets you against other players that are within 1 level of you and around the same population. Expeditions start when you reach level 5 and increase with the size of your city. Expeditions can only be played if your population is below the maximum allowed per happiness. Expeditions are refilled 1 per 30 minutes or you can use a legend to refill them. Honors are awarded for each type of expedition depending on how many you have won.
Expeditions are a great way to garner additional silver or XP. Population is better gained through the buildings as you gain additional XP at the same time.