chipboard is another name for a paperproduct that is between cardboard and cardstock.
![Smile](https://www.splitcoaststampers.com/forums/images/smilies/Smile SCS.png)
it is that thick pad that is on the back of a tablet...or like a jigsaw puzzle piece without the picture.
it has been popular for the past couple of years and comes plain/naked and white typically and you can cover it in patterned paper (using a glue stick) or paint it, ink it, etc. - very versatile and pretty inexpensive.
Other than through SU! there are currently big 'packages' of chipboard to be found in LSS and at your local M's and Joann's either in big sheets that you can run through a die cut machine, or already cut into shapes or alphas in various shapes, sizes and fonts.