When you visit more than one page at a time, you can use Tabbed Browsing to navigate the Web faster and easier. Tabbed Browsing lets you open tabs, each displaying a web page, within a single Firefox window. You don't have to have several windows open to visit several different web pages. You can open, close, and reload web pages conveniently in one place without having to switch to another window.
Notice that both pages are within view in a single browser window, with a tab open for each page. To toggle between pages, simply click on a tab (or press CTRL + TAB on the keyboard).
To close one or more tabs, right-click on a tab and choose Close Tab or Close Other Tabs, or click the "X" at the right of the tab.