Links you open in Safari on your iPhone or iPad may open new tabs, but not every link does. That’s fine until you realize that you have oodles of old tabs open, making it difficult to find any particular tab. In iOS 27 and iPadOS 27, tap the Tabs button, touch and hold Done, then tap Close All [number of] Tabs. This closes the tabs in the current Tab Group, so check that you have the group you want before closing them.
Cleaning these up won't make your device run any faster because these tabs aren't loaded into memory if you haven't used them for a few minutes. But if you dislike clutter and you're finding it difficult to locate the things that are useful to you this could be easier than closing all of them one-by-one.