What Do Facebook Notification Symbols Mean?
From comments to "likes," friends use Facebook to reach out to each other in a variety of formats. Facebook lets you know about each incoming communication with a notification or alert that flashes up on the banner at the top of the Facebook screen.
Notifications for new Timeline posts and comments left on your status updates appear in the upper right corner of any Facebook screen, just above the globe icon. Click the globe icon to open a pull-down box that contains a summary of each notification.
The new message symbol appears immediately to the right of the globe icon, in the top right corner of your Facebook screen. The symbol consists of two overlapping square text bubbles. When you click on the icon, your most recent message conversations appear in a drop-down window along with a short preview of the message. The thumbnail picture of the friend with whom you are messaging also appears next to the message. Select "See All" to view all your messages on the main screen.
When you receive a new incoming friend request, a notification appears just above the symbol of two overlapping heads, located immediately to the left of the messages symbol. Click on the symbol to see the thumbnail and name of the person who wants to friend you. To see the full request, just click on the name of the sender.
All new notifications are indicated by a red square or rectangle over the appropriate symbol. The small white number in the middle of the box represents how many new notifications you have. For example, a red squate with the number "5" inside of it located over the messages icon tells you that you have five new unread messages.