A crochet twist stitch wraps the yarn around a previous stitch to create cables, which are stitches that slant to the left or right. The stitch is also referred to as a front post stitch or back post stitch.
A post is the tall, vertical portion of a stitch. For a front post stitch, the hook enters the piece from the right side of the post, wraps under the post and then comes back to the front at the left side of the post. For a back post stitch, the hook enters from the back, rests over the top of the post and then is inserted to the back again. Because these stitches are worked around the post rather than into it, they create a loose stitch that easily twists into a cable.