This is a big one.
Facebook collects and infers an astonishing volume of data about its users, which it then uses to charge advertisers to target them with ads.
It does, however, offer some control over these settings — letting you cut down on what data it holds even if you can't stop ads entirely.
From Settings, navigate to "Ad Preferences" to access a dashboard.
The first menu is "Your interests," a list of all the things Facebook guesses you like from your activity then uses to target you with ads about. You can delete all of these.
Then there's "Advertisers you've interacted with." These include companies whose apps or websites you might have visited, whose ads you've clicked, or who uploaded contact lists to Facebook that include you (they may have bought your information from a third-party data brokers). You can click X on each of these to hide all ads from those advertisers — but be warned, there's a lot of them.
Third is "Your information." This lets you control whether certain things — including your relationship status, your employer, and your education — can be used to target you with ads. If you don't want this happening, turn them all off.
Fourth is "Ad settings," a bunch more toggles on how Facebook may use your data to target you with ads, including whether Facebook can utilize data it gets from other companies about your off-Facebook activity, and whether ads can incorporate your social actions in ads. If you're feeling privacy conscious, again, switch it off.
Last is "Hide ad topics," which lets you hide ads about certain subjects — alcohol, parenting, and pets — either temporarily or permanently.