Apt-get is an advanced packaging tool for Ubuntu and other Debian-based Linux distribution, used primarily to install packages into the system.
Running the following apt-get command will automatically download and install the package and all it's dependencies.
sudo apt-get install package-name
If you are for some reason want apt-get to just download the packages and dependencies without installing it, simply add
-d switch to the command as the following.
sudo apt-get install -d package-name
To confirm that the package is not installed, you're presented with the following output when the command done executing.
Download complete and in download only mode