The aggregate of your interaction with sponsored content is sent to Mozilla (sponsored links you've seen, clicked on, and how many times you've clicked on them). Your browsing history is never sent, either in whole or aggregate. It also sends your region, country, state, and county, but not your IP or anything that could uniquely identify you.

Since you aren't being identified, nor can you likely be identified, it's privacy respecting. Other advertisers attempt to build a uniquely identifying profile on you where they grab as much information as they can. When compared, Pocket looks a lot better than every other advertiser.

Regardless, I'm not comfortable with Pocket, so I disable it. I can't disable advertisers tracking me.

Here's the actual quote about search:

Firefox by default sends search queries to your search provider to help you discover common phrases other people have searched for and improve your search experience if your selected search provider supports search suggestions... Learn more, including how to disable this feature...

...

If you enable "Improve the Firefox Suggest Experience," we and our partners may also receive your search queries.

So it sends search queries to get search suggestions. I didn't see it mentioned one way or the other, but I'm assuming Firefox doesn't send any personally identifiable information with it, though the server probably can track you somewhat with your IP address.

Sending queries to partners is optional.