Fair use is when you site where you got the information from. Fair use is a way of adding work from other websites to your own, but you can only use part of the information and have to site it.
Piracy is when you illegally copy or use someone's work without permission. If you copy something from the internet that is not a public domain without asking permission, it is piracy.
Plagiarism is when you take someone else's work and pass it on saying it is your own. Printing a drawing and selling it to other people saying it is your own is plagiarism.
Digital footprint includes all the pictures that you have posted or someone else that has posted with you in it. It also includes the comments that you have posted on your own pictures or on other pictures. The comments made about you are also included in your digital footprint.