Lollipop (Android 5.0)
I know many of us might have come across this star on the status bar and asked them self this question.
What is the star in the Android 5.0 status bar, alongside the Wi-Fi symbol?
www.nairaland.com/attachments/5562714_star1_pngfd1ea6e8101a1efc98b1c9de4c78fe95

Here is the answer to the question..

Priority interruptions
Lollipop introduced the concept of “priority notifications”: These notifications rise to the top of the notifications screen, and you’ll continue to receive auditory or vibrate alerts for these notifications even when you have all other notifications muted.

If you’d like to be alerted only to these sorts of notifications, tap Interruptions. From this screen, you can choose to limit the sorts of notifications you’ll be alerted to, and whether you want to set some quiet hours.

First, set your priority preferences by tapping “When calls and notifications arrive.” A menu pops open with three options:
Always interrupt allows all notifications through—everything from calls to texts to app updates
Allow only priority interruptions will only alert you of certain kinds of notifications—calls, messages, events, and reminders. You can pick and choose which of these you want to be alerted to.

Don’t interrupt turns off all alerts for all notifications.

For the sake of this example, we want to limit alerts to only priority interruptions, so choose “Allow only priority interruptions” from the menu. Once you do that, it’s time to choose which kinds of notifications you want to give priority to. Toggle the Events and reminders, Calls, and Messages sliders accordingly, based on your preferences. For this example, I’m switching all three to the “on” position so all three kinds of notifications receive priority.

Priority interruptions lets you continue to receive audio alerts for certain kinds of notifications while silencing others.

If you decide to allow calls and messages through as priority interruptions, tapCalls/Messages from, and choose whether you want to receive notifications for calls from anyone, from starred contacts only, or from all your contacts but nobody else (“Contacts only”).