To open a new tab, tap on the button at the bottom right of the tabs tray.
How do I open a tab? Open a new blank tab
Tap the Sync icon to view your open synced tabs.
There is a separate tabs tray for viewing and opening your synced tabs. Once you’ve set up your free Firefox Account on Firefox for Android, you can sync your bookmarks, logins, open tabs and browsing history between devices.
Tap the Private browing icon to view your open private tabs.
There is a seperate tabs tray for your private tabs. You can also view sites in Private browsing mode if you don't want Firefox to remember your browsing or search history. The number indicates how many open tabs you have. Tap the tab icon next to the address bar to visit the tabs tray. All of your open tabs are stored in the tabs tray.