Royalty free refers to a type of license that gives you permission to use a stock image in certain ways. Royalty free means you are not required to pay a royalty each time you use an image.
Generally, royalty free images are images that are available under a non-transferable, non-exclusive, perpetual, worldwide, multiple-use sub-license.
“Let me just start off by saying you are an AWESOME TEACHER your tutorials are BOMB dude! I have learned so much from watching you it’s truly awesome.”
“I have learned so much in such a short time, I can’t imagine how much time it would have taken me to learn all I did without photigy!”