Twitter's new feature called 'Hovercards' is set up to be a fast and easy way to get information about a user without needed to leave your current page or work with additional tabs. Just move your courser over to the user's name or avatar and the hovercard will pop up. The hovercard besides showing you the information, gives you the interact with the user.
"On any timeline, as its namesake suggests, Hovercards are cards which appear when you hover over a username or avatar. The cards display additional information about the person and allow you to interact with them while staying within the context of your page.
One way we've found these cards to be useful is to find out more about retweeted people and follow them right there. You can also see more information with an expanded view of the card.
Sending direct messages to people you follow will also be possible with Hovercards so you can interact with tweeters without having to move off the page."