"Copyright is a form of protection provided by the laws of the United States (title 17, U. S. Code) to the authors of “original works of authorship,” including literary, dramatic, musical, artistic, and certain other intellectual works." [US Copyright Office, Copyright Basics, p.1]
It is important to understand copyright law to make sure you're not accidentally copying something you shouldn't be, and to ensure that you know when and how you can use other people's works as a part of creating your own.
Here are some straightforward (and in some cases, fun!) educational resources that will help you learn more about copyright.
The University of Texas Crash Course is particularly helpful. The "Own Manage Share" section will teach you how to manage your own copyright protected works and the "Building on Others' Creative Expression" section will teach you how to ethically and legally use the works of others.