As a copyright owner, you have the option of retaining your copyright completely, selling or licensing it to another entity (eg: a publisher or distributor), or releasing it to the Public Domain. If you want to retain your rights, but not have to field requests for specific routine uses, a public license is a great way to go! There are many options for licensing your work, but two of the most popular are Creative Commons and, for software, GNU.
Creative Commons licenses can be applied to any type of work, and are a human- and machine-readable way to say what your work can or cannot be used for. GNU licenses act similarly but are for software and related material.
Open Access: Open Access (OA) refers to freely available, digital, online information; generally scholarly literature. Open Access scholarly literature is free of charge and often carries less restrictive copyright and licensing barriers than traditionally published works, for both the users and the authors. Although Open Access can be used to describe non-scholarly resources like Wikipedia or Khan Academy, OA is usually reserved for scholarly work. Please remember: although OA resources are free to the user, they are not free to produce, host or develop.