A creative commons licence can allow you to use content that has already been created and incorporate it into your own work. Anything that is created is automatically protected by copyright. That means every piece of audio, video and text content you see online is already protected, unless someone has waived the copyright.
Copyright dictates who can share and use the content. If you want to share or otherwise use that content you have to obtain the creator’s permission.
If a content creator wants others to use their work but does not want to have to personally give permission to every individual who wants to do that they can use creative commons. The creator can apply the creative commons licence to their work and this overrules the automatic copyright.
Often there are conditions or rules to the creative commons licence. These rules are called creative commons elements. One that is most often used is that you have to acknowledge the person who produced the work as the creator of the content. This is called attribution.
Another commonly used element is known as non-commercial, which means that no one except the original content creator is permitted to make money from the content. For example you could print a creative commons image onto T-shirts and give them away, but you are not allowed to sell them.
Another element is ‘no derivatives’. This means the original content cannot be changed by anyone except the original creator. So for example if non derivatives applies you cannot take an image and process it through Photoshop or similar software to change the image.
Share alike is another element and this means any new content that incorporates the creative commons content has to carry a creative commons license too. So for example in this case you could use creative commons images in a video, but the video has to be made available subject to the same licence conditions as the creative commons images used within the video.
For more information on creative commons go to creativecommons.org. You can also search for creative commons content using search.creativecommons.org.