Shared is the group of tabs available to all users within the same Single Space. The Shared Space will allow users to browse the web together while in the same space. By moving tabs into a shared space, they can quickly communicate ideas to each other, and keep shared context on the conversation.
The primary group tabs remains on the left side as the user expects on any window. Tabs in the personal group can be dragged left to right onto the shared side, and will appear viewable by all users in the space. This is a maintained state, if you leave the space and come back, it remains the same.
When the user prompts the action bar or clicks the "+", the default will be to place the tab on the personal group, though the Action Bar will present a secondary option to automatically render the new tab inside of the shared group.
overview of shared space tab bar
When users are looking at the same tab, their individual icons will hover over the tab, giving others context on what everyone's consuming and what they're conversing over. If the individual isn't on a shared tab, their icon will return hovering over the Room
icons indicate what tabs people are looking at when in the shared tab space