Copyright
What is copyright?
Copyright is the right to use something (that is not necessarily on the internet). If you have copyright to something (image, photo, program, text) then it means that you can use that thing and no one else can use it without your permission. Respecting copyright may not be practical right now but if you get into the habit of using any image you find, you may run into serious trouble later down the road. You can use content that other people have made if they are in the public domain, meaning that the owner has allowed anyone to use the persons's work. Copyright does apply to unpublished works. Copyright protects work once it is created. International copyright doesn't exist.
If you notice someone contrasting the Copyright rule and taking images you have Copyright to without permission, a trusted elder or more specifically a teacher or an office administrator must be thus INFORMED. Here is the list of countries that respects the copyright of citizens.
Images
To avoid copyrighted images when searching on Google Images, select the "Search tools" button on the top center of the page. Then select "Usage rights" and click "Labeled for noncommercial reuse with modification" or "Labeled for reuse with modification", the first or second from the bottom. The images you now see are legal to use in accordance with copyright laws.
Text
If you come across a neat piece of text on the internet, you should not copy it word for word into your document. You can either rephrase it (also known as paraphrasing), or credit the original creator of that piece of text.
More Information
For more information regarding copyright, visit: https://www.copyright.gov/fair-use/more-info.html