There are 4 main areas in IP (intellectual property) law. These are: patents, copyrights, trademarks and trade secrets.
Patents: Protect an invention.
Copyrights: Protect artistic expression.
Trademarks: Protect brand names and symbols.
Trade Secrets: As long as you don't tell the secret, it stays protected.
(Example: the Coca-Cola formula is a trade secret.)
For authors, the most relevant area of IP law is copyright. Here are some of the basic things you should know.
What is copyright?Copyright is a property right which insures that someone else will not take your artistic expression and claim it as their own.
What does it cover?Copyright covers various forms of artistic expression. This includes music (both composition and recordings), dramatic works (plays, dance, opera), visual arts (painting, sculpture, illustration), and film/TV. Of course, the most relevant category for writers is written expression, which is also covered by copyright.
How long does coverage last?This is a tricky question because the law changes frequently. (The running legal joke is that length of copyright follows the "Mickey Mouse rule" in that coverage is extended continually so that lovable cartoon mouse will always be copyrighted.) A more specific answer can be found in the FAQ section of the U.S. Copyright Office website.
How do you get a copyright?The minute you write that last sentence and put down your pen, your work has gained certain rights under the copyright laws. This is why you don't need to tell agents or editors that your work is copyrighted because they already know that. Caveat: while ownership of the copyright is automatic, you may not be able to collect all the damages if you don't register it.
How do you register a copyright?You can register with the U.S. Copyright Office. Registering preserves some rights that you might not otherwise get, such as the right to sue for statutory damages (a fixed amount per work) and attorney's fees.
Does this mean that if you do all these steps and someone copies your work, the Copyright Police will go after them?Sorry, but that's not how it works. First of all, there isn't really a copyright police (yes the FBI deals with copyright matters, but usually in the case of large scale criminal infringement) and the copyright office doesn't enforce copyrights. You're probably wondering what the point of copyright is if it isn't enforced. What copyright means is if someone copies your work, you can take them to court and sue for damages or get an injunction. (An injunction means that the offending party must stop doing what they are doing.)
Take-home Message: Copyright is a property right to your work which you own automatically. By registering it, you give yourself evidence of having created that work. If someone copies your work, you can sue for damages or get them to stop their infringement.