"Works in the public domain are those whose intellectual property rights have expired, have been forfeited, or are inapplicable... public domain works can be freely used for derivative works without permission." - wikipedia.org/wiki/Public_domain
"A Creative Commons license is used when an author wants to give people the right to share, use, and even build upon a work that they have created. CC provides an author flexibility (for example, they might choose to allow only non-commercial uses of their own work) and protects the people who use or redistribute an author's work, so they don’t have to worry about copyright infringement, as long as they abide by the conditions the author has specified." - wikipedia.org/wiki/Creative_Commons_licenses
Find freely available and permissibly licensed, video, audio, and text for use in your presentations and projects.
Be sure to check the license information on all linked content. The linked material has been chosen as examples of Public Domain and Creative Commons Licensed works, however, it is the researcher's obligation to determine any use restrictions when republishing or otherwise distributing materials from the linked sites.
While public domain status generally applies to works that have aged out of copyright protections, there does exist the option to designate new content as public domain. Choosing to designate your own original works as public domain will waive all copyrights and related rights that you have over your work. The Creative Commons organization provides a tool publishing a public domain notice along with your works.