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