How do I find add-ons for packages when using the command line?

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http://askubuntu.com – My question is a little bit different from others already asked, I think. I've already searched for answers, but I didn't find anything related. For example, I always installed K3B via Terminal with the following command "sudo apt-get install k3b". It always worked, of course. One day, I decided to install it via Ubuntu Sofware Center and, to my surprise, there were a few Add-ons I didn't know about. I checked some of them to be installed as well because I found them useful. Now, here's my question: When we try to install a software via Terminal and this software has add-ons, how do we know (HowTos)