Copyright

The mere fact of being the author of an article grants two types of intellectual property rights: moral rights and exploitation or economic rights, also known as copyright. Moral rights are non-transferable and do not expire.
Exploitation rights include rights of distribution, reproduction, public communication and derivative work. These are transferable to third parties, with or without any remuneration. 
Transfer of exploitation rights to third parties can be done in two ways: by assignment and by licence. In the case of assignment, there is a transfer of ownership of these rights. In the case of licence, the right to use or exploit the object protected by intellectual property is granted under certain conditions that may include financial compensation.
One of the critical aspects of academic publications is that journals often require authors to transfer the exploitation rights of the published work. To protect and preserve copyright regulation, Creative Commons licences were created at the end of the 1990s. The objective of these licences is to establish a standardized model that protects the intellectual property of the authors, allowing its reuse under specific conditions.
Creative Commons licences contemplate 4 possible conditions:
 
Attribution
 
(BY)
 
The licensee has the right to copy, distribute and display the publication and publish derivative articles as long as he/she acknowledges and cites the article in the manner specified by the author or licensor.

Non-commercial

 
(NC)
 
The licensee has the right to copy, distribute and display the publication and publish derivative articles for non-commercial purposes.
Non-derivative publications
 
(ND)
 
The licensee only has the right to copy, distribute and display verbatim copies of the publication and does not have the right to produce derivative articles.
Share alike
(SA)
 
The licensee has the right to distribute derivative publications under a licence which is identical to the licence governing the original publication.

And depending on how they are combined, they give rise to 6 types of licences:

Attribution

CC BY

Attribution - Share Alike

CC BY-SA

Attribution – Non-derivative Publications CC BY-ND
Attribution – Non-commercial CC BY-NC
Attribution – Non-commercial - Share Alike CC BY-NC-SA
Attribution – Non-commercial- Non-derivative Publications CC BY-NC-ND
 
All the resulting licences require a minimum attribution or recognition. The condition of the share alike (with the same licence) and that of the no-derivative are incompatible with each other, although it is possible to dispense with both. The non-commercial status is optional.
 

More information: Creative Commons.