New features of twitter - Activity and @username which have been in news since some time were added to my account today.
Mentions tab has been replaced by @username. As @username timeline includes your @mentions, it also provides Tweets marked as Favorites, the latest Retweets (of your Tweets), and your new Followers. It also have the choice of showing only the mentions.
While the Activity tab provides Favorites, follows, retweets, and more by people you follow. So we can know what our followers are doing with their new follows etc.
Some of you might still not be seeing these features as twitter is rolling out these new features starting with a small percentage of users. You can send feedback about these features by sending a Tweet to @feedback with the hashtag #Activity.
Follow me on twitter @vasudevg