I see a lot of people using it, but, what exactly is it? Where would I get it? Do I make it, etc.

I've never used it, but heres a bump.

It is a lot like royal icing, but the actual color flow mix is supposed to make it harder and shinier than if you just used royal icing. Basically you make the mixture stiff so that you can first do and outline of your picture. Then you thin it way down and flow/run in the colorflow into your outline. You have to do it quickly because it starts to crust quickly It takes a couple of days to dry, but it dries hard. You can stand it up if you want. You can buy the mix from your craft store. Wilton makes it, I dont know if anyone else does. better directions for this method are in the course 2 Wilton book. I have a couple in my photos (spartan, and face of baby in my babyshower cake)

color flow is awsome! most of my cakes are done with color flow. i dont know if im allowed to post a link to my site so that you can see some examples so i wont. the other poster is correct in his/her discription of color flow. i would only add that you can use any image you want, from a coloring book, party decoration (to match the party) or whereever you might find a picture that you like. you tape that down to something like a cake board. wilton instruction say to then tape waxed paper over the image. i was told by steven stellingwerf (if you know who he is) to use cellofane instead. the stuff you would use to wrap a gift basket. anyway, if you use the cellofane, your image will almost never stick and/or break as it sometimes can with waxed paper. i buy holiday printed cellofane on clearance after just about any holiday for next to nothing.
then you outline with stiff, thin it and fill in. its fun, and looks awsome.
i did cakes this weekend with a stand up barn and a texas shape that i raised off the cake with mini marshmellow under the image. oh, i also had a sarugo cactus forest with all the cactus on lollypop sticks standing up.
anyway, you can do alot with it.

HTH

So do you make icing and then mix the color flow in? I really don't get it...