One main advantage of a Linux distribution over Microsoft Windows and Apple Mac OS is the presence of the “package manager”, the father (fathers actually, since there are many package managers) of the App Stores we now commonly find on smartphones.
The default repositories configured on the package managers are usually managed by the same company or team that created the distribution in use, Canonical in the case of Ubuntu, and generally they are sufficient to manage any software that we may need, but some time it may be necessary to activate an additional third party repository to be able to install a specific software or receive updates more rapidly for some common applications.
Ubuntu
Update Mplayer on Ubuntu
Since Ubuntu is not a rolling-release distribution, programs like Mplayer do not receive any major update, beside bug-fixes, until each new release of the distribution itself.
Here it is a guide on how to keep Mplayer updated on Ubuntu.
Update VLC on Ubuntu
Since Ubuntu is not a rolling-release distribution, programs like VideoLAN VLC do not receive any major update, beside bug-fixes, until each new release of the distribution itself.
Here it is a guide on how to keep VLC updated on Ubuntu.