A garter stitch (gs) is the name used to describe one row of knit stitches followed by a row of purl stitches. The garter stitch is often used to keep the edges of knit from rolling. In other words, if you are knitting along and you come to the end of your project a row of purl stitches at the end would keep it from rolling. If you are purling along, a row of knit stitches at the end would keep it from rolling. Often patterns begin and end with a few rows of alternated purl and knit stitches, or the garter stitches, for this reason.
The ewrap stitch can effectively be substituted for the knit stitch to form the garter, alternating a row of ewrap followed by a row of purl. Are you wondering what this looks like? You are in luck. Here is a photo of garter stitches done alternating the ewrap and the purl.
Rows 1, 3, 5, = ewrap
Rows 2, 4, 6, = purl