In simpler terms................

"Fair use" means that you can use someone else's picture on the internet for some things without asking their permission first. For example, if you are making a school project, writing an article or reviewing a book, you may use someone else's picture to help explain your point. However, you can't use a lot of the picture or use it to sell things, and you have to make sure that your use doesn't hurt the owner's ability to make money from their picture. If you're not sure if it's okay to use a picture, it's best to ask someone who knows about the rules first."