I do not know how to open the bottom panel of Gnome which shows the currently opened background applications and notifications and so on...
Usually I move my mouse to the bottom and sometimes the bottom panel shows up, sometimes not. I guess I am making something wrong.
Also I tried to find a shortcut for this (using the mouse, especially on a notebook is not the best solution) but I did not find a hotkey or some settings in dconf to do so.
I searched nearly half an hour via google but was not able to find an answer :/
By default (on my box, it can vary by distro and version) I think the keyboard shortcut is Super+M - this can be set in Keyboard Settings under shortcuts:
You can also open it by moving the mouse to the bottom of the screen, and then push (as though you are trying to move the mouse off the screen) and it should show. (I actually find this a problem as it opens all the time so use this extension to stop it).
Note that with Gnome 3.16+ this behaviour I think has been changed so that notifications show in the calendar etc: https://help.gnome.org/misc/release-notes/3.16/.