Published author here. In the UK, copyright exists as soon as you put pen to paper. It protects the right to print and distribute your work. There is no need to register it, although it is good practice to include a statement of your ownership of the copyright on publication. When you agree a publishing contract, you're typically granting your publisher a licence to print your words, but the legal ownership of the copyright remains with you. Copyright lasts for the whole of your lifetime, plus 70 years after your death. After that, the work is in the public domain and anyone can print and distribute it without paying a fee to the author's estate.
Copyright protects the words you wrote, in the order you wrote them. It is not possible to have copyright of an idea (so for example, when JK Rowling wrote Harry Potter, she was not infringing the copyright of Jill Murphy who wrote The Worst Witch, or Ursula Le Guin who wrote A Wizard of Earthsea).
Some extremely successful writers use other forms of IP protect\ion to protect phrases and words they have created. For example, "Harry Potter" is a registered trademark, and I believe quite a lot of the invented names and language around the Harry Potter universe are also trademarks. These are rights that have to be individually registered and regularly renewed. This is a specialist area and you would need a trademark lawyer to help you. It's not a form of protection that's really worthwhile unless your sales are huge and there are movies, merchandise etc involved too.
Hope this helps and good luck!