Twitter markets the feature as an "engaging and highly visible way to share your brand story with compelling video creative across Twitter's massive audience." It operates in a similar way to Facebook's Suggested Videos or Suggested Posts, in that it will sit between legitimate content on Twitter.com or the official apps and will attempt to catch your eye every time you visit.
It's no surprise that the company calls the spot its "most valuable advertising real estate." When brands buy the placement, which sits between the first and third tweets, they'll own it for 24 hours and you won't be able to escape it (like you would a Promoted Tweet). Twitter says the feature is already rolling out to a number of selected partners in the US and will expand globally "in the coming months."