If you look closely, you'll notice a row of small symbols running across the top of your screen. Knowing what they mean can help you gain helpful information at a glance:
Cell Signal Strength of cellular network (if you're out of range, “No service” will appear).
Airplane Mode All phone, Internet, and Bluetooth capabilities are
Carrier and Network Type Your carrier's name and type of data connection: LTE, 4G, 3G, E, or GPRS.
Wi-Fi Call Making a call via a Wi-Fi network.
Wi-Fi Strength of Internet connection over a Wi-Fi network.
Do Not Disturb All incoming messages, calls, and notifications are
Personal Hotspot Your device is providing a personal hotspot for another device.
Syncing Your iDevice is syncing with iTunes.
Network Activity Your device is processing a request.
Call Forwarding Call Forwarding is turned on.
VPN You have secure access to private data via a virtual private network.
TTY Your device is set to work with a TTY machine for hearing and speech impairments.
Orientation Lock You've locked the screen in portrait orientation.
An alarm is set.
Location Services An app or system setting is tracking your location.
Bluetooth When grey, Bluetooth is on but the phone is not paired with a device. When blue or white, Bluetooth is paired.
Bluetooth Battery Battery level of a paired Bluetooth gadget.
Battery Status Shows battery level or charging status.
AirPlay Your device is connected to Apple TV or another AirPlay-enabled device.