Copyright is a portion of intellectual property law that protects the creative expression of ideas for a limited amount of time. The purpose of copyright law is to incentivize creative people to continue making creative things.
Trademark law is a portion of intellectual property law that helps to identify where goods come from so that consumers in the open market don't get confused or deceived. Consumers prefer certain brands over others, and the law tries to ensure that they feel confident that expected quality continues with a certain brand.
Trademarks really refer to things like titles, logos, or a specific characteristic of branding that is unique enough to signal to consumers that a product comes from a specific source.
Copyright protects the work itself, like an entire book, a painting, a song, etc. In order to enjoy trademark protection, you need to express an idea in a sufficiently creative way and record that expression in a tangible medium, like written on a piece of paper, typed in a word document, paint on canvas, a transcription of a musical composition, a recording of an audio performance, etc.
Copyright holders enjoy six exclusive rights of exploitation over their creative work. Reproduction, Distribution, Adaptation, Public Performance, Public Display, and (in the case of audio recordings) Digital Audio Transmission.
If someone else exploits your work in one of those six ways, he or she has infringed your copyright.
Historically, there was a list of requirements before you could enjoy copyright registration, like registering with the Copyright Office and making sure the Copyright Notice was on display. While those are still best practices, they're no longer necessary. Your work is copyrighted as soon as your original idea is creatively expressed in a tangible medium.
There are a couple of key phrases here. You must express an original idea and fulfill a modicum of creativity.
So, ideas that haven't been expressed yet can't be copyrighted. This gets tricky for some forms of art like dance, yoga routines, or temporary sculpture, like chalk or sand art. A lot of artists in these genres are now finding ways to make a more permanent expression of their work (like putting it down on paper first) and then creating the temporary versions second. There's been a lot of attention in the courts recently about whether graffiti on buildings or tattoos on people count as fixed for copyright purposes.
Then there's the creativity. Facts aren't considered original ideas. Formulas aren't considered original ideas (including recipes). Content that exists in the public domain also can't be copyrighted. The public domain is the classification given to creative works whose copyright protections have lapsed.
Compilations of these copyrightable things are tricky, too. Compilations can enjoy copyright protection, but it really only extends to the creativity required to form the compilation, like layout, design, etc.
As I mentioned above, if you haven't yet expressed your idea, and someone else takes it, you're out of luck.
If you've expressed your idea, and the copyright has automatically attached, you have what we call a legal claim available to you. What you do with that legal claim is up to you.