Creative Commons Liscensing allows photographers to indicate what types of uses to allow. All types of creative commons liscensing ensure creators receive credit for their work, allow creators to retain copyright while giving others the opportunity to use their work, and work internationally, lasting as long as applicable copyright lasts. When using Flickr, it's important to understand the different types of liscenses so users can determine which suits their needs.
One type of creative commons liscense is the Attribution Liscense. This means that others can use, distribute, modify and copy work (even commercially) as long as credit is given for original work and derivitive works that have been created. Attribution-Noncommercial Liscense allows people to use works under the same conditions as the Attribution Liscense, but commercial use is not allowed.
Attribution No-Derivs Liscense gives users the right to use, distribute, and copy only exact copies of the original work. Credit must be given and no changes can be made.
Attribution-NonCommercial-NoDerivs is the most restrictive of the main liscenses. Users can download work to share, but commercial use is not allowed, no changes can be made, and credit must be given.
Attributions-ShareAlike Liscense lets others change and build upon work (even commercially) as long as they give credit and liscense their modified creations under the same terms. Any derivitives of the original work will have the same liscense. Attribution-Noncommercial-ShareAlike Liscense is the same, but commercial use is not allowed.