Ubuntu (and most other linux distributions) have a slightly different way of installing programs and applications. It has an app store, similar to Android and iOS, you can search for Firefox (and other apps) from in there. If I'm not mistaken, Ubuntu searched and notifies you for updates regularly.
The philosophy of Ubuntu (and most other linux distributions) is that you don't need to go to a bunch of different sites to download your software, you can just download all your software from the "app store".
And all of these tools are GUI's (so 'point and click'-based), so you don't need to open a terminal, if you don't want to.