Facebook has the potential to display your personal information to people you don't know well. In addition, trolling or cyberbullying can become an issue on Facebook. In these cases, the best option may be to unfollow someone, which stops the user's posts from appearing in your News Feed, or to block the user completely from your account.
Unfollow to Block Posts on Your News Feed
Step 1: Log in to your Facebook account and go to the News Feed on your Home page.
Step 2: Locate a post by the user you want to unfollow and click the down arrow in that user's post.
Step 3: Choose Unfollow [Username] from the drop-down list to stop seeing posts in your News Feed from the user.
Block Someone in Settings
Step 1: Click the down-arrow in the menu bar and choose Settings from the drop-down list.
Step 2: Choose Blocking from the left sidebar and type the name or email address of a user in the Block users box. Click Block, and Facebook searches for accounts that match your search term.
Step 3: Find the user that you want to block in the Block People pop-up window that appears and click Block, without clicking on the user's name or picture.
Step 4: Confirm that you want to block the user by clicking Block [Username].
Step 5: Note that the blocked user's name appears on the Manage Blocking page. Click Unblock to remove the block from the user.