Right-click on the coloured square -> ungroup tabs if you accidentally group them. Right click on the tab -> unpin tab if you accidental pin it.
(You can also ungroup and unpin by dragging them)
Groups are useful if you have a lot of tabs open and want to, you know, group them together based on a topic or something. This is especially true for those that do not know how to use bookmarks and keep 8 gorillion tabs open (I'm not one of them, but I've heard they exist.) Pinning is another feature like this, for tabs you use a lot it'll be easier to find them if they're pinned.
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thanks lol, i was in the middle of a game and couldn't check the settings until just now