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

To check your notifications:-

For Android:

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

1. Tap on Notifications icon  in below menu bar.

For iOS:

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

1. Tap on Notifications icon  in below menu bar.