Here are the first things to know about copyrights.
1. What is a Copyright?
A "copyright" is a form of intellectual property protection that grants exclusive rights to the creators of original works. Some of these rights include to right to reproduce, the right to create derivative works, and the right to publicly display your work, amongst others. The copyright holder enjoys these rights and can license the rights as he or she pleases, including transferring or selling the copyrights in a particular work to another party. In other scenarios, like a work-for-hire, a creator foregoes his or her copyrights to his or her work. In those instances, the owner of the work is the person or entity that commissioned the work. This often requires a written, signed agreement.
2. What is Copyrightable?
Not every imaginative or inventive idea is copyrightable. Sometimes those works fall under the scope of trademarks or patents (both different forms of intellectual property protection than copyright protection). Other times, a work is not copyrightable for a different reason like being unoriginal, commonly known, or derivative. So it's important to know whether your work is copyrightable to begin with. The U.S. Copyright Office says federal copyright protection exists for (1) original works of authorship that are (2) fixed in a tangible medium of expression. So your work must be sufficiently original and must be memorialized in some way - whether by photograph, video, or being put in writing. As far as what's eligible for copyright protection, it's a wide range of creative expressions, including literary, artistic, musical, and dramatic works. Architecture, sound recordings, and motion picture/audiovisual works are all copyrightable as well.
3. Copyright Registration
As stated in the previous section, copyright protection is automatic upon creation of an original work that is fixed in a tangible medium. That's it! You'll enjoy the rights to profit from your work for the duration of your copyright term (more on that in the next section). But what about having to register your work with the Copyright Office? Copyright ownership does not require registration. Just because you haven't registered the work does not mean you do not own the copyrights. However, registering your copyright with the U.S. Copyright Office provides additional benefits, including "prima facie" evidence of ownership and recovery of certain statutory damages. Basically, having the copyright registration tilts any ownership dispute in your favor from the outset because there is notice on record of your claim to ownership vis a vis your registration. Does this mean you automatically lose if you don't have a registration and the other party wins? Not necessarily, but it does increase the burden of proving ownership to a court. So deciding when to register your work often comes down to how much you feel your work is at risk of infringement by another party. This becomes more important as the cost or value of your work or production increases.
4. Duration of Copyright Protection:
Copyright protection lasts for the life of the creator plus 70 years. So a copyright owner can still profit from his work (or body of work) for almost two generations after his death. Often, that money funnels to his heirs or his estate.
For joint copyright ownership, the copyright lasts 70 years from the death of the last author. So if there are three screenwriters who jointly own the copyrights in a scripted show, the copyright would expire 70 years from the death of the last remaining screenwriter. For anonymous works, pseudonymous works, and works made for hire, the protection lasts even longer. The copyright expires 95 years from publication or 120 years from creation for unpublished works - whichever is shorter. If, for instance, you're a business contracting work-for-hire IP designs, this term might apply to those works. In each case, when a copyright term expires, that work falls into the public domain and is available free for the public to use. You can source public domain works through websites like Creative Commons or by searching the internet for public domain available resources.
There's obviously so much more to unpack regarding copyright law, but these four topics should provide you a good starting to point towards understanding how copyright law actually works.