Does youtube or any other website receive ownship of the copyrights to your original work if you upload your work on to their website for public viewing?

When you create an account on YouTube, and many other websites like YouTube, you are asked to read and sign an agreement.  You will need to read that agreement to determine if you "assign" your copyrights to YouTube when uploading the work.  Assignment is the legal term used when you transfer rights in something you have to another.  You can ask YouTube to show you the agreement or by going to your account you may be able to see it online.