Are you doing it as a whole row, multiple rows, or within one roe like k2, p2?
If you knit every row you get garter stitch. If you purl every row you also get garter stitch. If that is what you're doing it will be harder to tell the difference.
If you knit a row, then purl a row you get stockinette which looks like the smooth knit v's on one side and bumpy on the other.
Each stitch has a purl side and a knit side and they do look different at the top.