What happens when I click a Like or Share button on external websites?
The Like and Share buttons on other sites let you show your friends when you're interested in something. In order for your action to appear on Facebook, you must be logged into Facebook at the time you click the button.
When you click the Like button, it turns lighter in color. On Facebook, a story will appear on your Timeline and may appear in News Feed, just as if you liked something on Facebook.
When you click the Share button, a dialog will pop up allowing you to add a comment or adjust your audience before posting. On Facebook, a story will appear on your Timeline and may appear in News Feed after you click Share Link in the dialog.
In some cases, when you like things off Facebook, like a movie, athlete or business, this connection works in the same way as when you like a Page on Facebook. It'll appear on your Timeline, you may receive messages or updates in your News Feed, and you may be associated with the connection in Pages, ads or social plugins.
You can remove a like or share from your private activity log.