The status bar of the phone is located at the top of the page while on the Lock screen or when on the Settings home screen. The status bar displays information regarding signal strength, battery, and whether or not things like the alarm or wifi are enabled.
This is an example of the default status bar:
This is an example of the status bar with wifi, bluetooth, alarm enabled:
If no SIM is inserted, or no service is available there is no icon displayed. When your phone has service there is 1-4 bars displaying the quality of the connection.
The battery level is always shown on the top right of the status bar. It includes a numerical % as well as a corresponding battery icon. While charging you will see the lightning bolt instead of the battery icon. (learn more about the battery)
Wifi is OFF by default, and no icon is displayed. When ON you'll see the Wifi icon. The bad connection icon indicates that you are connected to a network that isn't working. (learn more about wifi settings)
Bluetooth is OFF by default. If enabled, the bluetooth icon is displayed the status bar.
(learn more about how to enable bluetooth)
If there is an alarm enabled, you will see the alarm icon in the status bar.
(learn more about how to enable the alarm)
Disabling Status Bar
You can also disable the status bar on the lock screen in the settings. To do so:
Settings > Preferences > Display > Toggle "Signal & Battery"