Gmail allows users to switch between multiple accounts for which earlier users had to click on Google navigation bar and then click on the ‘Sign in to another account’. But now with new update in Google can easily switch to your another account by clicking on either your name or profile image in Google navigation bar and then click on 2nd account.
You won’t see this 2nd account option if you will access any other service like Google Reader, Google Plus, Google Docs etc.
You can also click ‘Add Account’ to add new Gmail account. See how to use mulitple Sign-in feature in Gmail via your cellphone.