Google has introduced multiple sign feature to mobile version of Gmail. When the users go to the bottom of the Gmail web app, they need to tap the email address they are logged into the Gmail which brings forth a menu enabling the users to switch between different Gmail accounts, or sign into a new account or even sign out of all the accounts.
Users also get the option to edit their settings in the mobile version of Gmail, which happens through the settings icon in the menu bar. Users can choose a mobile specific signature for their Gmail account, which can be formatted and can be used to convey to other users that you have a smartphone as well. 
About the signatures, the Gmail blog says, “We know that autocorrect and other mobile spell-checks can be frustrating as you are typing on the go. Let your friends know that you are responding via your mobile phone so that they understand why you might have sent a message that you are meeting for “monitors” and not “mojitos”. It’s an easy way to make them understand why your message might be short or have a few typos.”
For quite some time, the desktop version of Gmail supported multiple sign in feature but the same was not available for the mobile version of Gmail. Google is quietly adding more features from its desktop version to the mobile specific web app, which shows they care about their mobile users.
Those who use a bookmark to access Gmail on their mobile Browser will need to update the bookmark since the URL has been changed by Google to support the multiple sign in feature.