Free Online Resources are resources that are available online but are not always open, so you may not be allowed to change or revise them to suit your needs. For those resources that do not fall under the public domain, it is best to use them by linking to the resource through your Learning Management System and sending your students to the specific site and not reposting the information.
Works in the public domain are not protected by copyright and you are free to use the entire work however you choose. It can be difficult to determine if something is in the public domain or not. There are several useful tools to help you determine if the material you are interested in is in the public domain.