In notifications you can see the following information: friends event, activity on your wall, activity on your post, mentioned event, and received a new message.

To check your notifications:-

For Android:

You receive your notifications as push notifications but you can check all received notifications at any time.

1. Tap on the Notifications icon  in below menu bar.

For iOS:

You receive your notifications as push notifications but you can check all received notifications at any time.

1. Tap on the Notifications icon  in below menu bar.