Every time you surf the Internet, your activities are tracked by a host of commercial operations and governments. The depth of information they accumulate on you is staggering and will at the very least expose you to marketing and advertising targeted to your online behaviour patterns.
If that concerns you, consider installing Privacy Badger, which is currently only available for Chrome and Firefox, from the EFF (no, not that one – the non-profit “Electronic Frontier Foundation”) from their website at https://www.eff.org/privacybadger.
Privacy Badger blocks spying ads and invisible trackers, it learns as it goes along and you can tweak how it handles particular sites.
Note: If one of your apps or extensions stops working or starts behaving strangely, you may need to change the Privacy Badger controls or even temporarily disable it.