One of the most powerful tools on Facebook, the like button not only communicates your support of activities, brands, articles and products to fellow users, but also to Facebook and third parties. The like button lives on nearly every piece of Facebook content: status updates, photos, comments, brands timelines, apps and even ads.

However, you ve probably also seen Facebook like and share buttons on external sites: shopping, news publications, mobile and social apps, and ads. These sites are utilizing Facebooks social plugins. When you like something outside of Facebook.com, it appears on your timeline, where friends can comment on the activity.

When Facebook expanded this functionality outside of Facebook.com, it opened up a rich social layer that most social networks had never before imagined. On the other hand, keep in mind that Facebook keeps track of your like activity and uses it to improve the quality of ads on the site. If sharing that kind of data makes you nervous, you re not alone. Just be mindful that Facebook can share this behavioral data with third parties. For more information, see Facebook s full data use policy.