The "youtube" button allows you to directly embed the "embed" code from youtube into a post in here and will resize it to fit the screen. If you have a video on youtube you want to share, click the share button and then choose the embed button, copy the code and come over here and click the youtube button to insert it into the post and paste the embed code where the cursor is, in the middle of the BBCode tag...like this:
[youtube]<iframe width="640" height="480" src="//www.youtube.com/embed/RrTTsqyxiTY
" frameborder="0" allowfullscreen></iframe>[/youtube]
the media button allows you to insert all sorts of media like sound clips, videos from any source, google maps, etc...
just insert the url of the media between the BBCode after you click the media button to see if it works
here is a song
here is a google map