When you are the creator of a creative work, you have protection under the law so nobody else can take your work and claim it is theirs. This protection is offered at the federal level, so if you have a case of copyright infringement in California, it is handled by a federal court, not a state court. Protection for written works and some audio work is offered under a copyright.
The concept of infringement can be confusing, but the U.S. Copyright Office, which regulates copyrights, explains it occurs when someone tries to take ownership of your work or uses it without your permission. This includes printing it in any form or distributing it in any way. You should know there are some exceptions where someone could use your work without your permission. However, exceptions are limited.
You should always register your copyrights as soon as you produce and publish your work. While you get copyright protection as soon as your work is published, registering it offers additional protections because there is a formal record that you are the copyright holder.
If you find someone has violated your copyright, then you may be able to take action. Infringement claims are usually considered a civil matter. This means you can sue for damages, but the person is rarely punished in a criminal manner. In addition, law enforcement will usually not be involved. You have to take the case to court.
In some cases, though, it could be a criminal matter. In that case, you would contact the FBI for assistance. This information is for education only and is not intended as legal advice.