Every week it never fails, any site with more visual examples of the design element is the easiest and sometimes quickest way for to fully grasp the concept of it.
This website provides information on the elements of design, including texture, and how important it can be to interior design, which I find interesting. It is truly incredible how much these elements can influence our daily lives outside of digital media.
I like this website because it describes repetition in detail. I like the examples it has as well. Also, I like on the sidebar how you can go to other principles of design.
this website illustrated some cool definitions that the book didn't. It even explained that with repetition the brain comprehends one and immediately knows the rest are identical.
This tutorial describes how to use lines with Adobe Illustrator. I thought this was really interesting to see how he creates a graphic pattern just using lines.