Gmail displays conversations and messages from one account at a time. If you set up more than one email account on your phone, you can easily switch between them.
From your Gmail Inbox, tap the Accounts and labels icon (at the upper-left corner of the Inbox header), tap the current account, then tap the account that contains the email you want to read.
The number of unread messages is displayed to the right of each account and folder.
Accounts and Labels Icon
Tap here to open a list of account choices and account labels.