So you can find things by "that spicy chicken recipe" instead of having to remember what it was actually called, or slog through a gazillion chicken recipes in your history when you realise that "spicy" was nowhere in the name. Basically stemming/thesaurus search on steroids.

It's quite likely to be opt-in as I imagine ingesting the sites you're looking at is a significant computational load. The translators are also opt-in, there's enough stuff inbuilt to detect languages but not to translate, you have to download those models first. And they're quite good btw.

Another thing I could see them offering is stuff like tl;dr bot. It's probably not for everyone, but I definitely can see that it can be a useful feature for many people.