We've added a feature that allows you to embed video and other similar media in your posts, blogs, etc. This means people can view it right in the thread instead of having to leave the site or open a new window. This is done for you automatically if the source allows it - and most news sites as well as YouTube and such do.
For example, here is the video for the song my (current) signature quote comes from:
To get this I just paste the URL and the board software figures out the rest. Here's what the URL looks like when I paste it (I have to do it this way to keep it from being converted, but I think you get the idea):
As you can see the source is clearly identified and clicking on the video will take you to the original source. The media will not show up in the preview, but it will when you post - and if you do NOT want this to happen there's a little checkbox below the post entry area to turn it off!