The Toolbar is an area of the screen just above the site that lists useful administration screen links such as add a new post or edit your profile.
The Toolbar contains links to information about WordPress, as well as quick-links to create new posts, pages and links, add new users, review comments, and alerts to available updates to plugins and themes on your site.
The toolbar can be turned on/off from the Toolbar option in Administration > Users > Your Profile, but It is no longer possible to hide the Toolbar when viewing the Administration Screens.
Note: If you have turned the Toolbar on in your profile settings, but still don’t see it on the front end of your site, it may be that your theme does not call wp_footer() in its footer.php file, or the Toolbar may be disabled by a plugin.