Today I was trying to upgrade my Ubuntu with sudo apt-get upgrade and accidentally typed Ctrl-Z while in the terminal and the upgrade stopped. After doing some research on this, here is what I found:
Pressing Ctrl Z in the terminal sends the process to the background causing it to pause until it is told to come back to the foreground.
Once the task is paused you can run another task and call the paused one later when it is needed. To check the paused tasks type jobs in the terminal.
To resume the process, you can type fg. If you have multiple tasks, then you type fg 1, fg 2 etc…