The word redundant applies to things that are unnecessary or could be left out. Calling a blank sheet of paper empty is redundant.
Teachers often tell students to avoid being redundant — meaning avoid saying something twice or more. Have you ever heard someone tell a story and repeat the same thing over and over? The repeated parts are redundant. Sometimes being redundant can make things clear, but it can also be annoying. Redundant can apply to anything that's overflowing or unnecessary. If a business has two stores on the same street, one is redundant. When you hear redundant, think "Too much!"