Priority Inbox which is a new feature launched for google apps users who use gmail, It automatically identifies your important email and separates it out from everything else, so you can focus on what really matters.
What are Important Markers In Priority Inbox ?
Priority Inbox displays different colored arrows to indicate different types of messages. A yellow arrow means that a message is important and unread. A grey marker means that the message is important and read or archived. A message Gmail has classified as unimportant has no marker.
Show or Hide These Markers follow the procedure below
If you prefer, you can hide these markers. Just go to the Priority Inbox tab of your Gmail settings and select the No markers option in the Importance markers section.
Gmail treats these markers like labels, so you can search for messages that are important by using the search operator ‘is:important’.