Lists have been a feature within Twitter for a long time, but they're buried under menus, making them inconvenient to use. However, they can be a great way to find relevant information quickly now that they're easily accessible. For example, a user could create a list of their favorite bands and quickly check if any of the groups have announced any concerts in their area, or they could build a list of relatives to keep up on family updates.

This feature is similar to the capabilities found in third-party apps like TweetDeck, but having swipeable lists in the main app will help more users take advantage. Desktop users can easily access lists, too, as they're prominently listed on the left toolbar.