Purl Crochet

In traditional crochet, the hook almost always moves through the work from back to front (away from your body). To achieve a smoother look (like when knitters change from knit to purl stitch as they turn their work), or showcase a design in some way, one can reverse the way every other row of stitching is worked. Here is an example done with sc (UK dc) to give you some practice. The concept can be used with most crochet stitches.

Insert hook through both loops of previous stitch from front to back, back-yo (wrap yarn in opposite direction than usual) pull loop yarn through

back-yo, pull through loops on hook
The 'right' or 'front' side of Purl Crochet will have distinct horizontal lines of stitching.
The 'wrong' or 'back' side of Purl Crochet will be quite smooth from typical viewing distance.

A video clip of me working to give you an idea of what I'm doing. Try this link if the first didn't work.

For a pair of longies, I worked in purl crochet every even row. The fabric above the design is hdc.

This helicopter was produced with the 'back' side of the stitches for a pullover. This looks like the 'front' side (inside of pullover), I don't seem to have a picture of the outside.
The sweaters for the twins were made using Purl Crochet. I chose the smooth backside of the stitches for the outside to showcase the floral designs.