The feature essentially shows some of the top tweets since the last time you used Twitter’s app. Marketing Land calls it “a major draw to the non-avid Twitter user. Instead of having to scroll through a timeline of every single Tweet, they’d be able to glean the best content instantly.”
In a November 2014 blog post, Twitter VP of product Kevin Weil writes:
We can use information like who you follow and what you engage with to surface highlights of what you missed and show those to you as soon as you log back in or come back to the app.
OMG, it appears Twitter is testing a Facebook-like algorithm for the Home stream called “While you were away…” pic.twitter.com/CpQQMLp0VO
— Eli (@EliLanger) December 31, 2014