The first part of our document's body is the navigation bar <nav>. The navigation bar usually contains the primary set of links for navigation in a website. Since we are building only a single page in this chapter, we can leave the navbar with only our page title.
The navigation bar is styled using Bootstrap. The class .navbar styles the respective element as the primary navigation bar of the page. The .navbar-inverse class adds a dark color to the navigation bar and the .navbar-fixed-top class attaches the navigation bar to the top of the screen using a fixed position. The contents of the navigation bar are wrapped inside a Bootstrap container (div.container). The page title is written inside div.navbar-header as an anchor tag with the class .navbar-brand, which instructs Bootstrap that this is the brand name/title of the application.
The Bootstrap navigation bar is highly customizable. To learn more about this topic, refer to W3Schools' Bootstrap tutorial: https://www.w3schools.com/bootstrap/ or Bootstrap's official documentation: http://getbootstrap.com/getting-started/.