Copyright is a set of rights owned by the creator of any fixed creative work, be it writing, art, music, software or recordings.
The copyright owner has the right to reproduce, create derivatives of, distribute, publicly perform, control the public display of, and publicly digitally transmit a recording of a creative work as soon as that work is created. There is no need to register for copyright. Copyright runs out after the life of the creator plus 70 years under current law.
CC licenses are used by copyright owners to allow others to use their work within specified guidelines, without affecting or damaging their copyright ownership of the work.
CC licenses do not reduce, limit, or restrict any rights under exceptions of copyright law like Fair Use, which allows educational use of works within specific parameters.
For more information about copyright go here: https://lib.uconn.edu/about/policies/copyright/
For more information on Fair Use go here: https://copyright.columbia.edu/basics/fair-use/fair-use-checklist.html