Copyright can be hard to understand and even harder in real life practice. The first huge fact that I learned was that even a particular object does not have the copyright symbol, it is still copyrighted. As long as you are taking someone else idea or work you are stealing. Also, there are two specific time periods to watch within copyright. They are when public domain starts. Copyright can protect the creator for their entire life and then 70 years after that. However, anything before 1963 is public domain or falls under another category. After 1963 you can follow the life rule plus 70. Anything from the government is also in public domain. None of materials form there are protected by copyright.
One big disappointment I learned about copyright is that you can only "sample" DVDs and show only a small clip. Growing up, I can remember is how excited we all got for movie day and seeing movies that go along with our lesson. This is actually breaking copyright laws unless the school has purchased the rights. Showing the whole movie to that many people is illegal and in reality you can only watch it by yourself or family.
There are other rules for using other pieces of work. It is only fair use if you use 250 words or less in written work. In a book or magazine you can only have one picture.
Finally, we have to remember the internet is not a public domain and we cant just take what we see. I invite you to look further into copyright by clicking on the links I read about below:
Taking the Mystery Out Of Copyright
15 Copyright Rules Every Student Should Know