Key Features of Open Licenses:
When it comes to OER the most typical open licenses used are Creative Commons Licenses.
Generally speaking, an open license grants permission to access, re-use and redistribute a work with few or no restrictions.
See: How to Choose an Open Licence and The National Forum Open Licensing Toolkit
The toolkit provides a detailed description of Creative Commons (CC) licenses, as well as a four-step guide to choosing, creating and adding CC licences to resources to make them OER.
Creative Commons (CC) is a non-profit organization permitting the sharing and use of creativity and knowledge through free legitimate means.
Creative Commons’ copyright licenses provide an easy and consistent way to give the public permission to share and use your creative work under your conditions.
The Creative Commons licenses are not an alternative to copyright, they work along with copyright enabling you to adapt your copyright terms to best suit your requirements.
Source: Creative Commons
The purpose of the CC Chooser from creativecommons.org is to help users choose which CC license is right for you and your needs -- Select the appropriate license for your work by filling in the fields you need, and you will receive formatted HTML code.