Today, Twitter rolled out Highlights, a feature that presents Android users with a twice-daily summary of the most important things happening on the network. Twitter creates the custom Highlights by analyzing "things like the accounts and conversations that are popular among people you follow, Tweets from people you're closely tied to, topics and events that are trending in your area or within your network, and people that are popular or trending among people you follow."
Highlights arrive via a push notification that takes users directly into the Twitter app; for instructions on how to turn them on, see the introductory blog post.
This is Twitter saying, "Hey, man, look at all the great stuff that happened while you were away. Please come back. Please?" It's a reminder that it exists and has interesting stuff for you to look at — or so it hopes. It's a way to gin up more engagement and more views (and ultimately to serve more ads), while keeping you up-to-date. Think of it as addition as service.