There are two stitches in knitting - the knit stitch and the purl stitch, and the back of the knit is a purl, the back of the purl is a knit. These two combine to make stitch patterns. Garter is knitting every row, stockinette is knit a row, purl a row. Rib stitch is knits and purls on the same row. Knitting a piece in stockinette will curl on the edges and at the ends. The usual cure is to knit garter stitch borders, because they generally won't curl. However, if something is narrow it may curl no matter how you're making it. It would help if we had a picture of what you're doing so we can identify where you're at.