.navbar-btn: When you want to place a Bootstrap button in a navigation bar, use this class to properly align it

.navbar-text: If you want to display some plain text, use this class to make it properly visible

.navbar-link: If you want to add a link, but not inside the .nav element, then use this class

.navbar-fixed-top: If you add this class to the parent of the navigation bar navbar, it will stick to the top of the browser window while scrolling

.navbar-fixed-bottom: This class fixes the navigation bar to the bottom of the window screen and it remains there while scrolling

.active: Adding this class to any of the <li> elements will highlight the link, as compared to other links