If you are a long time Windows user, the Ubuntu default graphical user interface which has the launcher on the left hand side may be a bit unfamiliar to you.
GNOME, which is a very common Linux graphical user interface, perhaps is better for new Linux user.
Cinnamon is a GNOME 3 fork that allow you to have a panel at the bottom of the screen with a classic Windows-like start Menu.
Like Ubuntu Tweak, Cinnamon is on an external repository, so we have to add it manually. Use the following commands in Terminal to install Cinnamon.
sudo add-apt-repository ppa:gwendal-lebihan-dev/cinnamon-stable
sudo apt-get update
sudo apt-get install cinnamon
After the installation, logout the current session and select Cinnamon on the login window as follow before logging in again.
Reference: Chris Hoffman – Install Linux Mint’s New Cinnamon Desktop on Ubuntu