People create original works all of the time. When they do, they may find that their work is so valued and desired that people replicate or disseminate their work in ways that the creator finds improper. So who does a creator protect his or her original works? This is where copyright law comes into play.
A copyright is a legal protection that prevents people from using, producing or distributing a creator's original work without the expressed consent and approval of the original creator. Without copyright law, original creators would be ripped off left and right, and there would be little incentive for someone to create original works since other people would simply replicate and use their work to profit.
That's a dystopian world we don't want to live in, and so copyright protections are critical. What do copyrights protect? Well, it's quite a wide range of original works. From literary works to musical scores; from dramatic works to choreographed pieces; and from audio and visual forms to architectural drawings; there are many things that can be covered by copyright protections.
There are also many original works or ideas that can't be protected by a copyright, and it is important for creators to know why that may be. For example, if your original work can't be defined in a "tangible" form -- such as an improvised speech -- then you can't copyright it.
The line can be difficult to define sometimes, and it behooves original creators to consult with an intellectual property attorney to ensure they are going about protecting their original work in the proper manner.