You'd specifically see it with tiling window managers like i3. I can put any container node of the window tree in tabbed, stacked, tiled horizontal or tiled vertical mode. So, I can have tabs of any mix of programs, I can change the mode to see all tabs at the same time, each tab can have subtabs or windows organized in any way I see fit, I can fullscreen any level, etc.

The handling of those tabs also fit with the rest of the window management, like putting marks on a container so new windows appear at whatever place in the window tree I wish (like having a shell to my left and all windows I'm invoking having them appear organized in an arbitrary manner in a window container to my right), etc.

I can keep going, but if you're not familiar with tiling window managers, I feel like probably none of what I'm saying is making any sense...