Creative Commons Licenses offer an alternative to the "All Rights Reserved" model of intellectual property that is created by default when a work is expressed (and thus falls under copyright law). The copyright holder can choose to publish their materials under Creative Commons licensing to increase its usage (and some would argue that this increases its value), to allow for collaboration with other content creators, and/or to meet aspirational goals of contributing to the "greater good" of society.
From YouTube: http://www.youtube.com/watch?v=AeTlXtEOplA
From YouTube: http://www.youtube.com/watch?v=-xVKqDqYS0U