File sharing is taking anything - a song, video, piece of software, etc - and making it available to others. That's perfectly legal, as long as you own the copyright to what you're sharing. It's the copyright issue that gets everyone in trouble.
If you create something yourself like a movie, write a song or take a picture, you own the copyright to that work. That copyright gives you the right to do what you want with it, whether you want to give it away, sell it or prevent others from using your creation.
Let's say you recorded an interview of Johnny Depp on the Today Show. NBC & the Today Show would own the copyright for that broadcast, so they would have the right to prevent you from sharing the clip or uploading it to Youtube. If NBC noticed the clip, they might contact Youtube and ask them to remove, it claiming copyright infringement.
I'm not telling you what to do, I'm just explaining it a little. If you're really interested in the legal end of it, google Title 17 of the U.S. Code. Loads of fun reading