Copyright can seem confusing. Although, in reality, it isn't. Simply put, if someone creates something, no one else can use it, without giving credit, and some kind of compensation. Meaning, you can't claim something is yours, if you didn't make it. Also, you want to use someone else's stuff, you have to pay for it.
Here's a great video over at B&H Photography about Copyright and Photographers Rights!
From the ACLU: