Means in your Generals the option to see it is unchecked and you need to go there to see what it says.

I don’t see a box at all for asking if I want them to ask my permission to close a tab on my computer. In the browser.

You mean there is nothing in General? Here's what mine shows. Look where the arrow points to.

You can easily undo a closed tab and reopen it in case you accidentally closed a tab. You can find "Undo Closed Tab" in the right-click context menu of the Tab bar.