I have a feeling this answer will depend on everyone's opinions and which design spec they follow. However, maybe it will give me a broader perspective.
I have a "panel" (as best as I can describe). It so happens to contain tabs in this instance, but may not always. It sits in my sidebar, but again, should be able to sit anywhere.
It's similar to the gaming.youtube.com example attached with the suggested/comments tabs and pane.
What is this called in GUI? A panel?
I tend to think so but then I see lots of examples of panels like this which are kind of like cards: http://foundation.zurb.com/sites/docs/v/5.5.3/components/panels.html
But is this just one example of a panel which has the fundamentals of: "Panels are often used to section window (browser window in my case) contents to ease visual organization."