Google Chrome's incognito mode is a feature that can be use for allowing private browsing which like you can open multiple gmail accounts on same browser.
When you open a window in incognito mode (Ctrl+Shift+N), your cookies from the standard session are no longer available and you can easily log in to a new Google account.
When you activate incognito mode then a new window opens, you can see the description and use of that window as "Pages you view in this window won't appear in your browser history or search history, and they won't leave other traces, like cookies, on your computer after you close the incognito window. Any files you download or bookmarks you create will be preserved, however.",
When you close the incognito window, all the cookies are deleted so you need to log in again the next time you browse in incognito mode. This trick can be used for any other services that allow multiple accounts, but you can only use two accounts at the same time: one in a standard window and the other one in incognito mode.
