Tapestry crochet is a method of crochet colorwork where the inactive yarns are carried inside the stitches that are being worked.
I was first introduced to this technique through the book Tapestry Crochet by Carol Norton (Ventura). I was drawn to both the dense fabric and by the fact that it allowed me to create color patterns.
One of my first projects where I developed my skills in this technique was this bag.
I used some orange rug yarn and hand spun Churro guard hair. The effect is really nice with the color variations in the Churro.
Essentially all you're doing is a very snug single crochet and the inactive color is carried inside the stitch. To change colors is done in the final yarn over and pull through.
Carol Ventura, the author of the book I learned from has set up a wonderful web site for tapestry crochet resources. There are videos and tutorials that can help you learn this great crochet technique.
I've published two bag patterns of my own that use this technique. My Waza Bag and my Past Times Bag. More are in the works.