Which icon are you referring to?
I see the following from left to right -
Facebook Messenger
Some kind of cloud sync service
Google Maps (asking for a review or suggesting info about your current location)
Battery icon (this looks out of place, is this battery saver?)
Location service scanning
Bluetooth
Notifications set to vibrate only
Alarm
For the first 4 (well, you could count the ... as a 5th, that indicates more notifications) you can pull down the notification shade to see what that notification is as well as what the additional ones hidden behind the ... are.