According to web dictionaries, the definition of the garter stitch is 'a basic knitting pattern in which every row is knit. The fabric looks like a series of ridges with flatter rows between, and looks the same on both sides. It is the most basic pattern in knitting'.
However, since on the loom we don't turn our work around, the garter stitch is performed by alternating the knit stitch and purl stitch on each row. The garter stitch is a perfect stitch for borders, scarfs or any flat panel, because it does not curl on the edges.