On create campaign there is an option under advanced settings to setup List Conditions based on the selected list. This can be used to send to a portion of a list that meets a specific list criteria. For instance lets if the list has a custom column called state. Using the list conditions system the list can be filtered by a specific state and when sending campaign would only go to the state specified in the list condition. This eliminates the need to create a new list first to filter by that criteria needed.