By hovering over the WordPress "W" logo, you can access information about WordPress, as well as the official WordPress documentation, which is even more extensive than the help pages that are provided here.
If you are an administrator or author of multiple websites (via WordPress Multisite), you'll see a link to "My Sites," which gives you easy access to all of the sites that you have access to. If you are only an admin/author on one site, you will not see this option.
The "+ New" link gives you quick access to adding new content, whether it's a page, blog post, news item/press release, etc.
Finally, if you hover over the "Howdy, [Your Name]" link on the right hand side, you'll be able to edit your profile (which includes your password, email address, etc.), and log out of WordPress.