When you browse the web normally, your browser will save information about the sites you visit. In addition to your browsing history, Chrome will remember usernames, passwords, and the contents of forms that you fill out.
A new Chrome window opens, with a darker color scheme to indicate that it's incognito.
Any browsing you do in this window won't be saved by Chrome. If you were signed in to any sites, those logins won't be recognized, and you'll need to sign in again. Once you close the window, its browsing history, cookies, login information, and form data will all be deleted.
However, private browsing isn't anonymous browsing. Websites you visit will still be able to log your IP address, and if you have a network administrator that can view your activity, they'll still be able to see it.
When you're done with a private browsing session, make sure to close the window. After a window is closed, and only after it is closed, all of its history is cleared.