Under "Your Facebook Information," select "Off-Facebook Activity."
A banner will preview some of the websites and apps that Facebook knows you've used. Click on the app icons to see a full list of those sources.
The full list will include third parties that shared your activity with Facebook in the past 180 days. Clicking "Clear History" will delete this information that Facebook has saved.
In my case, over 600 apps and websites had shared my browsing history with Facebook.
Toggling the switch next to "Future Off-Facebook Activity" will stop Facebook from saving your future activity to your account. However, it doesn't stop third parties from sending Facebook information about you.