Gater stitch has both sides made up of a row of flat sides of stitches alternating with a row of purl bumps. If you are knitting flat, then knitting every row (or purling every row) gives you garter stitch.
Stocking stitch has one side of flat (knit sides of a stitch) and the other side of bumps (purl stitches). The bumpy side looks a bit like garter.
Just turn your work around at the end of each row and work it, you will be doing the wrong side every other row, and the right side every other row.