The two new options are InVideo Programming and Call-to-Action Overlays. InVideo Programming will automatically add overlays to videos in order to get the viewer to watch the next video in a channel's list. The Call-to-Action Overlays will start out only available to advertisers, but eventually will be made available to all channel operators and allow them "to share more information about the content of your video, raise interest in your channel, or your own web site."
These updates are available now in the YouTube apps for Android and iOS and will be coming to the mobile website soon.
source: YouTube Creator Blog