Copyright is serious business! US laws protect the rights of the copyright holders, who may or may not be the creators of the content. Other countries also have laws that protect their citizens' works. The copyright police in the US are the FBI. Violations of copyright law have no legal defense.
Only the copyright holder has the rights to:
sell
distribute
edit (shorten, edit wording, remove language, change images, etc.)
decide how the material is used
Any form of created work is copyrighted if it is in a form that may be copied. These days, that means almost anything: written work, audiovisual work, artwork, photographs, music, recordings, etc. With 3D printers, this could become even more complex.
Works do not have to have a copyright symbol and date on them to be considered protected under the law.
Generally speaking, copyrights in this country expire 50-100 years after the creator's death. If copyright is not renewed, the material moves into the Public Domain and may be used by others.
Once the copyright has expired, materials are no longer copyrighted. Dover Publications, for instance, has books and digital images full of public domain images that can be used as needed.
All materials protected by copyright may be used by students if they follow certain rules for documentation:
All materials a student uses, whether copyrighted or not, must be documented appropriately.
There are different requirements for print and audiovisual materials.
Students may not plagiarize.
Owning a copy of a video or song does not give students the rights to use them in their presentations. For instance, if a student purchases songs from iTunes or another online service, he/she may not use that song in a presentation without written consent from the copyright holder.
Images need documentation immediately below the image as well as at the end of the student's work (Reference List).
Documentation may not say Google. Actual sites must be documented, not search result sites.
Include both internal (citation inside the student product) and external documentation (Reference List at the end).
Sources for copyright free materials include Creative Commons, Wikimedia Commons, etc. Creative Commons licenses tell you what you may use, how you may use it, and what documentation is required. You have to read and comply with the licensing requirements.
Google searches usually bring up copyrighted material.
Use your own creations! Write your own materials. Compose your own songs. Take your own photos. Create your own artwork.
It's stealing!
Companies now have bots to search sites online for violations of copyright. They may find out you used their materials. They have lawyers. You can be fined or worse! I know students who have paid fines and suffered consequences.
Your teachers will know. They are grading you.
You will know. You have a conscience to know right from wrong.
You are learning how to do work in the real world. You need good habits. Build them now so you won't get fired, fined, or jailed in the future.