U.S. copyright law grants the creator(s) of a work the exclusive right to make copies of the work, distribute it, display or perform it publicly, and make derivative works. For more information, consult the sources below.
The term open access is generally associated with academic publications, especially peer-reviewed articles. Open access publications do not require the reader to pay a fee in order to access articles. The Library databases page can connect you to the Directory of Open Access Journals which provides access to research journals from around the world.
By default, creators retain all of the rights accorded to them by U.S. copyright law. This is known as "all rights reserved."
However, creators may choose to license a work under a free/open license, which allows them to waive some or all of their rights. Some of the most popular open licenses are offered through the organization Creative Commons.
A work's license will tell you what exactly you can do with it. For example, Creative Commons licenses include:
These are typically used for licensing software code as an alternative to Creative Commons, but are occasionally used for other types of works.