I think that's a great explanation, Laurie
I guess this just started with me going through my favorites and noticing all of the different places and ways you can put your image on a card. All of my cards seem to have the same design, a block of stamped images in the middle with a stamped saying in the bottom right. My stuff was starting to look boring to me lol, so I really started paying attention to where other people put their stamped images on the card (called the layout or sketch of the card) and wanted to emulate them, so thus, the "sketch chalellenge" was born! Nothing formal, I just wanted something fun to do for myself and thought others would be intereste din it too.
So basically, you get out whatever paper, embelishments and stamps that you want to use to make a card but you put them on the paper using the "sketch " for the week. So, maybe I was doing the fishy friends set with this week's sketch. I would maybe put a blue strip across the lower section of the card and then stamp a fish on 2 different pieces of cardstock, and then I would tuck them behind the strip like the sketch is laid out.
I hope this is helping clear this up for some people, sorry about the confusion! The goal is just to get out some stamps and play and maybe get out of the rut , like me, of putting my cards together in the same way so they look the same all of the time. No pressure, just play around with it and see how it goes. Its all about having fun with our stamps, which sometimes we forget to do.