LisaB ran across a really good blog post explaining copyright. Attorney and law professor M. Scott Boone explains the basics of copyright protection here. http://kobowritinglife.com/2013/09/25/the-basics-of-copyright-protection/
If you are a writer, it is imperative that you understand copyrights. Although Boone doesn't address it in his post, disregard everything you've heard about Poor Man's Copyright. Mailing something to yourself does NOT equal registering your copyright, and does NOT give you any legal protection. I have heard that PMC has some legal standing in the UK, but it has NONE in the US.
Your writing is your blood, sweat and tears. Don't throw it away. Protect it like it matters to you.
PS: You're a writer. Don't confuse copyright and copy write. They are not the same things.