If you don't know what is a "free software" or "why you need it", worth spending some time watching the video from the FSF front page : https://www.fsf.org/?pk_campaign=video
Oh, yes, one more notice: that video is encoded using the Vorbis codec and stored in an Ogg container. Both are free software
. Surprisingly enough (?) Google+ is unable to share a link to them properly (say: by adding a thumbnail...). And some "media player" might even not support those formats without installing a "plug-in" (probably with some nice warnings in pop-up windows™ : "Are you sure?" "No, you don't want that?" "This is your last chance !" "This may broke your computer !!!"). Whereas, those players all support proprietary format like MPEG that are protected by patents, so requiring the payment of licensing fees to the patent holders... Freedom you said ?