Reverse single crochet is also known as Crab Stitch. Instead of crocheting from right to left, you crochet into the stitch left of where you just worked. It forms an attractive decorative edging. There are several videos on youtube demonstrating this stitch clearly.
Working left to right, insert hook in next stitch to the right, yarn over, and draw thread through. Thread over, draw it through two loops on hook. One reverse single crochet completed! This is also called a 'crab stitch'.