

GMail page now shows the opened sessions information at the bottom of the page. We can click the details link provided with that information to read the report of all the sessions and last activities done with our account.

This report is helpful in determining whether the account is opened from two places. The IP address information also provides insight whether the account is compromised.
The most important feature now GMail provides is the Sign out of all other sessions button on this report. Now we can just sign out of all other GMail sessions we may have opened from any other place by clicking this button. Only the session we are currently using is kept on and all others are logged off.
Now that is really secured.
Reference:
Official GMail blog post
With Regards
Tushar Joshi, Nagpur