The current Google Account is displayed in the header at the top of the Inbox. If you have more than one account, you can switch accounts to view the messages in each Inbox.
Conversations with new messages are displayed with bold subject lines. To read a message in a conversation, tap its subject line text.
A gray background indicates a read message.
indicates that you were copied on this message.
indicates that this message was sent directly to you.
The letter icon (or contact photo) next to a Gmail message allows you to select it and choose an action from the icons at the top of the screen.
The Favorite icon next to a Gmail message allows you to designate it as a favorite message.