Under the Creative Commons Attribution license, commonly abbreviated as CC-BY, you are free:
Under the following conditions:
See the human readable versions (with links to the full deed) at Attribution 3.0 Unported, or various other compatible versions for other jurisdictions and in other languages (please add links).
Attribution mandatory unless you indicate otherwise. First and foremost, CC BY requires that users keep intact all copyright notices on your work and provide, in a reasonable manner, your name (or the name of your organization) as the author, the title of the work, and the URL, if any, that you specify to be associated with the work. It is essential that you make it very clear how you wish to be attributed at the point of upload so that downstream users will know how to credit you properly. Further, under CC BY, you retain the right to request removal of attribution if you do not wish to be associated with a particular derivative of your work. Thus, if you become aware of your work being used in a derivative work or in any collection as permitted by the license, you have the absolute right to inform the creator of the derivative or collective work that you do not want to be identified as the author of the original work, and insist that your name be removed. This is an important layer of protection that many content producers find valuable and prevents them from being associated with works they believe are "lower quality" than the work they originally produced.
No endorsement allowed. CC BY, just like all CC licenses, also contains a “non-endorsement” clause. Specifically, this clause states that users may only use the credit required for the purpose of attribution, and may not assert or imply any connection with, sponsorship, or endorsement by you, without your separate, express prior written permission. In plain English, this means the user is not allowed to use attribution to make it appear that you in any way support or approve of their uses or adaptations of your work. So, for example, if a downstream user of your work is somehow implying that you are endorsing their derivative work, whether in advertising on a website or otherwise, that could constitute a violation of the license.
Your original remains unchanged. Because CC BY permits adaptations, some people worry that the work they create will be changed for the worse or somehow "ruined" by downstream users. It is important to remember that when users adapt your work, they alter copies of your work, not the original. Your original work will remain intact, and indeed, the adaptations based upon it will point back to your original work, if you require it, so that other users have access to your "higher" quality original.
Changes must be labelled. Finally, CC BY requires users to take reasonable steps “to clearly label, demarcate or otherwise identify that changes were made to the original [w]ork.” This means that users who adapt your work must tell the world they have done so, thereby letting other users know what changes were made by someone other than you.