The new iPhone app does just what Flipboard on the iPad did; collect stories from social media accounts as well as other sources and present them to readers in a visually pleasing format.
But there are significant differences. For one thing, the iPhone app works by swiping up and down, rather than the old format of turning pages from right to left. More importantly, the phone app introduces "cover stories". This new section learns from your interaction with content so that it can deliver stories that are most interesting and relevant to you.
The differences are part of a drive to distinguish between the lean-back platform of the iPad, which most people use before bed, and the lean-forward platform of the iPhone, which users are more likely to access on the go or standing in queues.