Gnome-Shell is a very different work-flow compared to the traditional desktops like the previous Gnome-2 interface.
You can see all your running apps by clicking the Activities menu option.
Fortunately, there is the ability to "extend" the interface through extensions
For example you can install "frippery bottom panel" to have a more traditional panel to choose your running applications
or you could have a "Dock" which appears and disappears on the right-hand side of the screen depending if you position your mouse in that area.
If you dont want to use extensions you could use tint2:
sudo apt-get install tint2
tint2 to your startup applications